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1 Descripción técnica de la alta disponibilidad de Microsoft® SQL Server™ 2005
Slide Title: Title Slide Keywords: Key Message: Title slide Slide Builds: 0 Slide Script: Hello and welcome to this Microsoft TechNet session, “A Technical Overview of SQL Server 2005 High Availability.” My name is {insert name}. Slide Transition: Data is a key component to the operation of an organization, and databases are among the most important services that Information Technology professionals provide to their organizations. This session will cover several technologies in SQL Server 2005 designed to increase the availability of the server, the databases on that server, and the data in those databases. Slide Comment: Additional Information: Christian Linacre Microsoft Cono Sur

2 Lo que vamos a cubrir Barreras para la disponibilidad
Falla o desastre del servidor de base de datos Error del usuario o de la aplicación Limitaciones de concurrencia de acceso a datos Slide Title: What We Will Cover Keywords: Key Message: Introduce the four main topics for the session. Slide Builds: 4 Slide Script: [Build 1] This session will start by covering several barriers to database availability. Although we can’t cover all availability barriers in a single session, we’ll cover those that may cause either server or database failure. We’ll also address how to protect your databases from user or application errors that may result in deleted or incorrect data. We will look at barriers that prevent concurrent access of data even when the database and data are intact but the data is being modified or the underlying structures are being altered. [Build 2] We will then talk about how failover clustering, database mirroring, and peer-to-peer replication in SQL Server 2005 can be used to help mitigate the effects of server failure or disaster. We will also compare these technologies to other high-availability alternates, such as replication, log shipping, and backup and restore procedures. [Build 3] Next, we’ll discuss how to configure SQL Server 2005 database snapshots to provide point-in-time reporting and quick data recovery in the event of accidental or malicious damage to the database.

3 Lo que vamos a cubrir (Notas)
Barreras para la disponibilidad Falla o desastre del servidor de base de datos Error del usuario o de la aplicación Limitaciones de concurrencia de acceso a datos [[Build 4] Finally, we’ll show you how to mitigate the effects of locking and blocking in OLTP environments by implementing the new optimistic concurrency controls in SQL Server You will also be able to optimize index operations by creating, altering, and dropping indexes online. Online index operations limit locking of the base table during the operation; therefore, transactions and applications do not have to wait until the operation is complete to read, modify, or insert data. Slide Transition: We’ll be discussing many advanced concepts today, and we won’t have time to explain many common terms. Slide Comment: Additional Information:

4 Experiencia útil Nivel 200
Sintaxis básica de T-SQL (Select, Actualización) Experiencia con procedimientos almacenados Familiaridad con los registros de transacciones y los procesos de recuperación Conocimiento de los controles de concurrencia Slide Title: Helpful Experience Keywords: Key Message: Helpful experience Slide Builds: 4 Slide Script: With this in mind, this session assumes you have some knowledge of SQL Server 7 and 2000. [Build 1] You need to know basic T-SQL syntax. For this session, you will really only need to understand the SELECT and UPDATE operators. [Build 2] You also need to understand how to run stored procedures and DBCC statements. [Build 3] In addition, you need to understand how SQL Server uses transaction logs to store transactions. It is important that you know the difference between the three recovery models and understand how SQL Server uses transaction logs in the recovery process. [Build 4] Finally, you need a basic understanding of how SQL Server handles locking and blocking. Slide Transition: Over the next 90 minutes, we’ll cover the five items listed in our agenda. Slide Comment: Additional Information: Nivel 200

5 Agenda Comprender las barreras de la disponibilidad
Recuperarse de una falla del servidor de la base de datos Recuperarse de un error del usuario o de la aplicación Vencer las limitaciones de concurrencia Comprender la duplicación de igual a igual Slide Title: Agenda: Understanding barriers to availability Keywords: agenda Key Message: agenda Slide Builds: 5 Slide Script: [BUILD1] We’ll start with a discussion of those items that may affect the availability of your database. You’ll learn about availability solutions and issues that affect availability, such as processing environment, hardware, software, malicious attacks, and natural disasters. [BUILD2] Once we’ve covered the barriers to availability, we’ll then discuss the options and features available in SQL Server 2005 that minimize their impact on your databases. We’ll start by covering clustering and then move on to examine database mirroring. Then we’ll compare these solutions to other high-availability solutions in order to see the advantages and disadvantages of each. [BUILD3] Next we’ll look at how snapshot technologies can be used to mitigate user or application errors. Snapshots provide point-in-time reporting and quick data recovery in the event of accidental or malicious damage to the data in a database. [BUILD4] We’ll close out the session by looking at data-access concurrency limitations. There are new features in SQL Server 2005 that can make the server more available in environments with heavy transaction processing. We’ll examine pessimistic concurrency controls that have historically been available in previous versions of SQL Server and then examine new concurrency controls, including optimistic concurrency controls and snapshot isolation. [BUILD5] We’ll close out the session by looking at peer-to-peer replication. We will see how peer-to-peer replication can be used to provide a hot standby of a replication publication. Slide Transition: To start, we should examine the business requirements that demand database availability. Slide Comment: Additional Information:

6 Factores de disponibilidad de la base de datos
Slide Title: Database Availability Factors Keywords: database availability Key Message: Explain the business factors that affect availability, including processes and expectations. Slide Builds: 0 Slide Script: Database availability is a complex concept. Many elements are evaluated in determining if systems are sufficiently available to meet an organization’s needs. Business requirements include consideration of business hours and locations. A longer workday and locations that span a large number of time zones require a different level of availability than a business with a shorter workday in a single time zone. In addition, business processes also impact the definition of availability. How business transactions are handled could affect whether the database must always be available or whether business can continue when failure occurs. User and management expectations also set different availability requirements on your organization. Slide Transition: Technology provides both solutions and challenges to availability. Slide Comment: Additional Information: ” Día hábil / zonas horarias Procesos de negocios Expectativas de los usuarios y de la administración

7 Soluciones de disponibilidad
DBMS Hardware Slide Title: Availability Solutions Keywords: availability solutions, DBMS, hardware, applications Key Message: Explain how features of hardware, applications, and DBMS software can address and mitigate the barriers to availability. Slide Builds: 0 Slide Script: Computer hardware, especially for servers, is becoming more and more reliable. This increases availability, but hardware can still fail at times. You should consider that it’s not only the server hardware that affects availability, also but network and client hardware. The Database Management System server software can also greatly affect availability. How the system accesses data, stores data, and maintains consistency and concurrency affects database availability, usually limiting it. DBMSs can also implement several features that help increase availability. The application software that accesses databases in a DBMS also affects availability. Properly programmed applications can increase availability by implementing good error checking, by monitoring the server connection and possibly failing over automatically to another available server, and by using small transactions to limit concurrency issues. The rest of the session will focus on SQL Server 2005 features that will increase availability of your data-management solutions. Slide Transition: Now that we’ve looked at the barriers to availability, let’s see how we can mitigate them with features in SQL Server 2005. Slide Comment: Additional Information: SQL Server 2005 Books Online: Topic: “Configuring High Availability” Base de datos muy disponible Aplicaciones Aplicaciones

8 Agenda Comprender las barreras de la disponibilidad
Recuperarse de una falla del servidor de la base de datos Recuperarse de un error del usuario o de la aplicación Vencer las limitaciones de concurrencia Comprender la duplicación de igual a igual Slide Title: Agenda: Understanding database server failure or disaster Keywords: Key Message: Introduce the next agenda item. Slide Builds: 0 Slide Script: In this section, we’ll discuss the options and features available in SQL Server 2005 that mitigate our barriers to availability. We’ll start by covering clustering and then move on to database mirroring. Then we’ll compare these solutions to other high-availability solutions in order to see the advantages and disadvantages of each. Slide Transition: Let’s start by looking at failover clustering. Slide Comment: Additional Information:

9 Clúster de conmutación por error
Conmutación por error de unos 20 segundos Ocho nodos Sin pérdidas del trabajo comprometido Soporta más servicios SQL Slide Title: Failover Clustering Keywords: clustering, failover Key Message: Explain that clustering is an effective, but expensive, solution. Slide Builds: 0 Slide Script: Failover clustering provides a hot standby server. By hot standby server, we are referring to the server that takes over database operations when the main server fails. SQL Server failover clustering is built on Microsoft Cluster Services, or MSCS. It can therefore take advantage of all the benefits that MSCS provides. If you are running SQL Server 2005 on Windows Server 2003, this means that you can now have eight nodes in your SQL Server clusters. MSCS provides for automatic failover in approximately 20 seconds, plus the time to complete the recovery process. SQL Server 2005 allows access to a database after all committed transactions have been written to disk but before the uncommitted transactions have been rolled back. This is faster access than SQL Server 2000 when failing over to a secondary cluster node. Microsoft Cluster Services does require special certified hardware. The special hardware requirement is a shared disk array and controllers that are certified by Microsoft for use in a cluster. Some of these products can be quite expensive. No committed data is lost since the clustered servers all share the same database file and transaction log. You will lose any uncommitted transactions because the secondary server initiates the recovery process on all SQL Server instance databases. SQL Server 2005 failover clustering now supports more SQL services. In addition to the SQL Server Service for OLTP databases, you can now use clustering for Analysis Services, Reporting Services, and Notification Services. Base de datos en clúster

10 Clúster de conmutación por error (Notas)
Conmutación por error de unos 20 segundos Ocho nodos Sin pérdidas del trabajo comprometido Soporta más servicios SQL You should also be aware that clustering uses shared disk arrays, so only one copy of the database exists. Clustering does not protect against disk failure nor does it protect the database from a disk controller card that writes bad data to the disk array. One more thing to be aware of is that you cannot actively use the database instance on the standby server, although other instances can be run on the standby servers. Slide Transition: As an example, let’s look at a two-node cluster. Slide Comment: Additional Information: SQL Server 2005 Books Online: Topic: “Database Mirroring and Failover Clustering” Base de datos en clúster

11 Implementar el clúster de conmutación por error
Arreglo de discos compartidos Clientes Red privada Slide Title: Implementing Failover Clustering Keywords: clustering, failover Key Message: Show the example and explain the components involved in a failover cluster. Slide Builds: 0 Slide Script: The best implementations of failover clustering use a second private network for the clusters so the server will not fail over in the event of a network hardware failure. Clients access a cluster virtual server that has its own name and IP address. The use of a virtual server prevents the clients from needing to manually reconnect if a node fails. You should note the shared disk array is a single point of failure. The shared disk array does create a distance constraint. Clustered servers almost always will reside in the same data center, making them susceptible to disasters, both human-made and natural. Slide Transition: Database mirroring is a high-availability solution that does not have a single point of failure. Slide Comment: Additional Information: SQL Server 2005 Books Online: Topic: “Database Mirroring and Failover Clustering” SQL Server 2005 Books Online: Topic: “Failover Clustering” Servidor virtual Red de latido Efectiva pero cara Servidores en clúster

12 Operaciones de reflejo (mirroring) de bases de datos
Menos de tres segundos Sin pérdidas del trabajo comprometido Máximo un reflejo por BD Redireccionam. transparente del cliente Slide Title: Database Mirroring Keywords: mirroring Key Message: Explain how database mirroring works and its advantages and limitations. Slide Builds: 0 Slide Script: Database mirroring is a new technology designed specifically for high-availability solutions without the drawbacks of clustering. Like clustering, mirroring provides a hot standby server and failover occurs faster than in clustering. Database mirroring can be configured to provide automatic failover. The automatic failover requires a third database instance to act as a witness server. It also requires the Synchronous with Automatic Failover option be selected. This option requires the transaction to be able to be committed at both servers before it commits in the principal database. This ensures that in the case of server failure the mirror has all committed transactions. You can use database mirroring using asynchronous transactions and no automatic failover for a warm standby solution. Database failover occurs very quickly with database mirrors, usually in less than three seconds. If the client application was programmed using ADO.NET 2.0, the client can implicitly fail over to the mirror. The ADO.NET libraries automatically perform this operation without the programmer needing to code it. If the client application is not programmed using ADO.NET 2.0 libraries, the application will need to programmatically handle the server failover. You will not lose any committed data if database mirroring is configured with synchronous transactions. If configured with asynchronous transactions, some committed data loss can occur. Using database mirroring in synchronous transaction mode for high availability will result in some performance impact. Transaction throughput, or number of transactions per second, will likely be minimally impacted. Transactional latency will be affected by the round-trip communication time between the two mirroring servers. If you are using asynchronous transaction mode, transactional latency will not be affected. You can configure a maximum of one mirror for each mirrored database. You can, however, mirror separate databases to different SQL Server instances on separate servers.

13 Operaciones de reflejo (mirroring) de la base de datos (Notas)
Menos de tres segundos Sin pérdidas del trabajo comprometido Máximo un reflejo por BD Redireccionam. transparente del cliente The database mirror is not available for any other use. It cannot be queried or used for reporting. You can, however, create database snapshots of a database mirror and use those snapshots for reporting purposes. Slide Transition: We’ll explore database mirroring in our first demonstration. Slide Comment: Additional Information: SQL Server 2005 Books Online: Topic: “Database Mirroring and Failover Clustering” SQL Server 2005 Books Online: Topic: “Overview of Database Mirroring”

14 demo Demo Configurar un reflejo de la base de datos
Crear un reflejo de la base de datos Establecer reflejos de la base de datos Acceder al reflejo de la base de datos después de una falla Slide Title: Demonstration: Configuring a Database Mirror Keywords: Key Message: demonstration Slide Builds: 0 Slide Script: In this demonstration, we will see how to configure a database mirror, establish the mirror, and have SQL Server 2005 access the mirror after a failure. Slide Transition: Let’s move on to the next section of our session. Slide Comment: Additional Information:

15 Agenda Comprender las barreras de la disponibilidad
Recuperarse de una falla del servidor de la base de datos Recuperarse de un error del usuario o de la aplicación Vencer las limitaciones de concurrencia Comprender la duplicación de igual a igual Slide Title: Agenda: Understanding user or application error Keywords: Key Message: Introduce the next agenda item. Slide Builds: 0 Slide Script: In this section, we’ll look at how snapshot technologies can be used to mitigate user or application errors. Snapshots provide point-in-time reporting and quick data recovery in the case of accidental or malicious damage to the database. Slide Transition: We’ll start by exploring the snapshot technology. Slide Comment: Additional Information:

16 Instantáneas de la base de datos
Mantiene los datos históricos Para generación de informes Salvaguarda los datos contra Errores administrativos Error del usuario Slide Title: Instantáneas de la base de datos Palabras clave: instantáneas de database snapshots, Enterprise Edition Mensaje clave: Introduce database snapshots. Compilaciones de la diapositiva: 0 Guión de la diapositiva: A database snapshot provides a read-only, static view of a source database as it existed at snapshot creation minus any uncommitted transactions. Multiple snapshots can exist on a source database, and they always reside on the same server instance as the database. Debido a que una instantánea de la base de datos proporciona una vista estática de una base de datos, una instantánea puede ampliar el acceso a los datos desde un punto en el tiempo específico. Por ejemplo, puede crear una instantánea de la base de datos al final de un periodo dado para informarlo posteriormente. Puede luego ejecutar los informes del final del periodo en la instantánea. Before doing major updates, such as a bulk update, you can create a database snapshot on the database to protect the data. If you make a mistake, you can use the snapshot to recover by reverting the database to the snapshot. Reverting is much faster than restoring from a backup; however, you cannot roll forward afterward. By creating database snapshots on a regular basis, you can mitigate the impact of a major user error, such as a dropped table. For a high level of protection, you can create a series of database snapshots spanning enough time to recognize and respond to most user errors. For instance, you might maintain 6 to 12 rolling snapshots spanning a 24-hour interval, depending on your available storage. Then, each time a new snapshot is created, the oldest snapshot can be deleted. Transición de la diapositiva: We have two examples to show how database snapshots work. Comentario de la diapositiva: Información adicional Libros en líneas de SQL Server 2005: Tema: “Database Snapshots” SQL Server 2005 Enterprise Edition

17 Cómo funcionan las instantáneas de la base de datos
Base de datos fuente Instantánea Página Página Se copió el 30% Slide Title: How Database Snapshots Work Keywords: snapshot Key Message: Explain that snapshots do not store all data pages and that the amount of disk space required depends on the amount of changes in the data pages. Slide Builds: 0 Slide Script: Look at the key first: Notice that the grey areas denote unallocated pages, while blue denotes the original page, and red the updated page. Blue arrows are used to show the read operation on the snapshot. The red boxes indicate data pages that have been updated. Notice that the snapshot is only storing original values for those data pages that have been updated. The blue arrows indicate what data pages are read during a read operation on the database snapshot. SQL Server will read the data from the source database when the data pages have not been updated after the creation of the snapshot. The space required by a snapshot depends on how many data modifications occur. Slide Transition: Now let’s look at a slightly different example. Slide Comment: Additional Information: SQL Server 2005 Books Online: Topic: “How Database Snapshots Work” Sin asignar Página original Página actualizada Clave Operación de lectura en la instantánea

18 Cómo funcionan las instantáneas de la base de datos
Base de datos fuente Instantánea Página Página Se copió el 80% Slide Title: How Database Snapshots Work Keywords: snapshot Key Message: Explain that snapshots do not store all data pages and that the amount of disk space required depends on the amount of changes in the data pages. Slide Builds: 0 Slide Script: This is a similar diagram depicting a database, potentially the same database, that has been updated more often. The two examples shown could be two different tables in the same database. One of the tables has been updated more than the other since the creation of the snapshot. This will likely be the case in most databases. Some tables are frequently updated—like an orders table—while some are rarely updated—like products sold or countries in which a company does business. Slide Transition: You’ll see database snapshots work in the following demonstration. Slide Comment: Additional Information: SQL Server 2005 Books Online: Topic: “How Database Snapshots Work” Sin asignar Página original Página actualizada Clave Operación de lectura en la instantánea

19 demo Demo Implementar las instantáneas de la base de datos
Crear una instantánea de la base de datos Acceder a la instantánea de la base de datos Recuperar datos a partir de una instantánea de la base de datos Slide Title: Demonstration: Implementing Database Snapshots Keywords: snapshot Key Message: demonstration Slide Builds: 0 Slide Script: In this demonstration you’ll learn how to create a database snapshot and how to access the snapshot. Then, we’ll see how to recover data from the snapshot. Slide Transition: Now that we’ve examined snapshot technologies, let’s move on to the next section of our session. Slide Comment: Additional Information:

20 Agenda Comprender las barreras de la disponibilidad
Recuperarse de una falla del servidor de la base de datos Recuperarse de un error del usuario o de la aplicación Vencer las limitaciones de concurrencia Comprender la duplicación de igual a igual Slide Title: Agenda: Working with data-access concurrency limitations Keywords: agenda Key Message: Introduce the next agenda item. Slide Builds: 0 Slide Script: In this section, we’ll look at data-access concurrency limitations. There are new features in SQL Server 2005 that can make the server more available in environments with heavy transaction processing. We’ll examine pessimistic concurrency controls that have been available in previous versions of SQL Server and then examine new concurrency controls, including optimistic concurrency controls and snapshot isolation. Slide Transition: First, let’s review pessimistic concurrency controls. Slide Comment: Additional Information:

21 Controles pesimistas de concurrencia
Base de datos SQL Server 2005 Slide Title: Pessimistic Concurrency Controls Keywords: concurrency controls, pessimistic, transaction, isolation Key Message: Explain how pessimistic concurrency controls work and their impact on availability. Slide Builds: 0 Slide Script: Concurrency controls were designed to help maintain data integrity. Without the controls, several transactions could update the same data and decision code in transactions could select inaccurate rows to update. Pessimistic concurrency controls are the default setting in SQL Server They were the only controls in SQL Server 2000 and earlier versions. Pessimistic concurrency controls require shared resource locks for SELECT operations. This means that updates can not occur while reads are occurring and reads can not occur while updates are occurring. The default behavior is to hold shared locks for just the duration of the SELECT operation. - SELECT requiere locks de recursos compartidos - Los niveles de aislamiento controlan el comportamiento de los locks compartidos

22 Concurrencia pesimista (Notas)
Base de datos SQL Server 2005 This behavior can be controlled by using different isolation levels. The transaction isolation levels control the behavior of shared locks. The isolation levels solve one or more problems that can occur while accessing data. They range from reading uncommitted data from memory, bypassing the exclusive locks on the rows on disk, and holding shared locks for the duration of the entire transaction. The isolation levels have different impacts on concurrency. Locking the rows for an entire transaction will prevent any updates from occurring until the transaction completes, thereby reducing concurrency and availability of the database. Sometimes it may be necessary for data integrity reasons to lock rows for an entire transaction. Slide Transition: In addition to pessimistic concurrency controls, SQL Server 2005 now has optimistic concurrency controls that handle shared locks in a different manner. Slide Comment: Additional Information: SQL Server 2005 Books Online: Topic: “Concurrency” - SELECT requiere seguros de recursos compartidos - Los niveles de aislamiento controlan el comportamiento de los seguros compartidos

23 Controles optimistas de concurrencia
Lista ligada Base de datos TempDB Fila 1: Datos XSN: 1 XSN1: Fila 1: Datos Fila 2: Datos Slide Title: Optimistic Concurrency Controls Keywords: concurrency controls, optimistic, transaction, isolation Key Message: Explain how optimistic concurrency controls work and how row versioning works. Slide Builds: 2 Slide Script: The transaction isolation levels that use optimistic concurrency controls are an optional setting. Optimistic concurrency controls are implemented by using row versioning. [BUILD1] First, let’s look at how row versioning works. Within each instance of Microsoft SQL Server 2005 and for databases enabled for row versioning-based isolation levels, the SQL Server 2005 Database Engine assigns a transaction sequence number to each transaction. Transactions start at the time a BEGIN TRANSACTION statement is run. However, the transaction sequence number starts with the first Transact-SQL statement after the BEGIN TRANSACTION or statement. The transaction sequence numbers are incremented by one. Every time a row is modified, the instance of the Database Engine stores a version of the previously committed image of the row in tempdb. Each version is marked with the transaction sequence number of the transaction that made the change. The versions of modified rows are chained using a link list. The newest row value is always stored in the current database and chained to the versions stored in tempdb. [BUILD2] As stated before, optimistic concurrency controls use row versioning. These controls are still designed for data integrity, but will allow reads of committed data while other transactions are holding locks that would prevent SELECT statements from completing. SELECT operations that use these concurrency controls do not use shared locks on the rows in the database, but instead use the row versions maintained by SQL Server when the controls are enabled. The different isolation levels for the optimistic concurrency controls control which row versions are accessed by SELECT operations instead of how shared locks are acquired and released. You will want to make sure that tempdb is optimized for performance and has enough disk space before you implement the optimistic concurrency controls. A heavily accessed database can place a significant load on tempdb for both performance and disk usage. SQL Server deletes row versions when they are no longer necessary to support any transaction or operation that requires them. This helps to limit how much space these use, but large transactions or very large numbers of transactions can cause SQL Server to store many versions in tempdb. XSN: 2 Fila 3: Datos XSN2: Fila 3: Datos Versiones de registros habilitadas - Permite lecturas de datos entregados SELECT usa las versiones de registros, no los locks compartidos Las versiones de filas tienen varios usos

24 Concurrencia optimista cont. (Notas)
Lista vinculada Base de datos TempDB Fila 1: Datos XSN: 1 XSN1: Fila 1: Datos Fila 2: Datos It’s also worthwhile to note that row versioning has several other uses. Row versioning is used for the inserted and deleted tables that are used by triggers. Multiple Active Result Sets, or MARS, sessions make use of row versions as well. ONLINE index operations, which we’ll discuss a little later, use row versions during their operations. Finally, row versioning is also used for row snapshots to implement the optimistic concurrency controls. Slide Transition: Another new transaction isolation level is snapshot isolation. Slide Comment: Additional Information: SQL Server 2005 Books Online: Topic: “Concurrency” XSN: 2 Fila 3: Datos XSN2: Fila 3: Datos Versiones de filas habilitadas - Permite lecturas de datos entregados SELECT usa las versiones de filas, no los seguros compartidos Las versiones de filas tienen varios usos

25 Nivel de aislamiento de la instantánea
Base de datos TempDB Slide Title: Snapshot Isolation Level Keywords: transaction, isolation, snapshot isolation, concurrency controls Key Message: Explain how snapshot isolation level works. Slide Builds: 1 Slide Script: Snapshot isolation level is a new transaction isolation level that uses row versioning and does not require shared locks to read data. Snapshot isolation level enables transactions to read committed data that is being modified by other transactions. Snapshot isolation level will allow reads of committed data as the data existed at the time the transaction started. The data may be modified while the snapshot isolation level transaction occurred, but any read operations will read the older, committed data. You can be sure that all read operations in the transaction will be accessing the exact same data. [BUILD1] To enable snapshot isolation level, you must use the ALLOW_SNAPSHOT_ISOLATION database option. This does not change the default concurrency control or transaction isolation level. The option simply activates row versioning in the database. Once you select this option, all INSERTs, UPDATEs, and DELETEs cause SQL Server to create row versions, regardless of whether there are any transactions using snapshot isolation level. SQL Server does not know whether a transaction will start before any updates will complete, so it must maintain row versions just in case a snapshot isolation transaction starts. You can enable transactions to use snapshot isolation level by using the TRANSACTION ISOLATION LEVEL SNAPSHOT session command. This command only works if you have previously enabled the ALLOW_SNAPSHOT_ISOLATION database option. Slide Transition: You can also use read committed snapshot isolation. Slide Comment: Additional Information: SQL Server 2005 Books Online: Topic: “Working with Snapshot Isolation Level” Versiones de filas habilitadas Opción de base de datos ALLOW_SNAPSHOT_ISOLATION Opción de sesión TRANSACTION ISOLATION LEVEL SNAPSHOT - Lee datos a partir del momento en que inicia la operación

26 Lectura comprometida (Instantánea)
Base de datos TempDB Slide Title: Read Committed (Snapshot) Keywords: transaction, isolation, read committed snapshot isolation, concurrency controls Key Message: Explain how read committed snapshot isolation level works. Slide Builds: 1 Slide Script: Read committed transactions can also be used to reduce concurrency limitations. These transactions read committed data at the time of the statement in the transaction. Different statements in a transaction may get different result sets for the same read operation. This is the default for the pessimistic concurrency controls as well, but read committed snapshots do not acquire shared locks. These transactions can read the latest committed data even if it is being modified by other transactions. [BUILD1] To enable read committed snapshot isolation, enable the READ_COMMITTED_SNAPSHOT database option. You can use the TRANSACTION ISOLATION LEVEL READ COMMITTED session option to use read committed snapshot transactions. You should notice that the command does not specify to use the snapshot version of the read committed isolation level. If you have enabled read committed snapshot for the database, all read committed transactions use read committed snapshot. Technically, you do not even have to use this session option, since read committed is the default transaction isolation level. Slide Transition: Another new feature of SQL Server 2005 is Online Indexing. Slide Comment: Additional Information: SQL Server 2005 Books Online: Topic: “Isolation Levels” Versiones de filas habilitadas Opción de base de datos READ_COMMITTED_SNAPSHOT Opción de sesión TRANSACTION ISOLATION LEVEL READ COMMITTED - Lee datos a partir del momento en que inicia la operación

27 Operaciones de indexación en línea
Slide Title: Online Index Operations Keywords: index, indexing, online index, online indexing Key Message: Explain the benefits of ONLINE index operations. Slide Builds: 0 Slide Script: OFFLINE index operations were the only options available in previous versions of SQL Server. The key difference between an ONLINE index operation and an OFFLINE index operation is that during an ONLINE index operation, the underlying data in the table is still accessible during the indexing operation. The table is accessible for both read and update operations. In fact, if you are creating a clustered index, any non-clustered indexes are still available for the optimizer to use. The new clustered index is not used until its creation operation is complete. SQL Server continues to access the old table heap until that time. Of course, a non-clustered index is not available during any operation being applied directly to that non-clustered index. There are also a variety ONLINE index commands, such as: CREATE INDEX, ALTER INDEX, and DROP INDEX. In addition, the ALTER TABLE command can be used if you either ADD or DROP a Unique index or ADD or DROP a primary key with the clustered index option. Slide Transition: Let’s take a look at an ONLINE index operation. Slide Comment: Additional Information: SQL Server 2005 Books Online: Topic: “How Online Index Operations Work” Operaciones de indexación en línea Índice creado Tabla - La tabla es accesible para lectura y actualización Los índices no cluster están disponibles durante la creación del índice en clúster

28 Operación en línea de indexación en clúster
CREATE CLUSTERED INDEX index_name ON table_name … WITH (ONLINE = ON) Fase de preparación Usuarios concurrentes Fuente (Tabla) Objetivo (Indice en clúster) Bloqueo Slide Title: Online Clustered Index Operation Keywords: index, indexing, online index, online indexing Key Message: Explain how ONLINE index operations work. Slide Builds: 0 Slide Script: When an ONLINE CREATE CLUSTERED INDEX operation is started, there could be many transactions reading and writing data to that table. Let’s look at what happens and what access is available during an ONLINE clustered index operation. [BUILD1] The first phase is the preparation phase. During this phase, SQL Server will prevent new transactions for a short period of time while it creates the new target index structure and some temporary objects to be used during the creation. Slide Transition: The next phase of an ONLINE index operation is the build phase. Slide Comment: Additional Information: SQL Server 2005 Books Online: Topic: “How Online Index Operations Work” No se permite ninguna actividad Instantánea definida Metadatos actualizados Se creó un nuevo índice vacío Bloqueo de IS S lock

29 Operación en línea de indexación en clúster
Fase de creación Usuarios concurrentes Fuente (Tabla) Objetivo (Indice en clúster) Bloqueo Slide Title: Online Clustered Index Operation Keywords: index, indexing, online index, online indexing Key Message: Explain how ONLINE index operations work. Slide Builds: 0 Slide Script: During the build phase, transactions can use the table again while data is sorted and copied into the new clustered index. SQL Server will keep track of the rows that are modified during the initial copy of data pages and refresh those data pages in the index. Slide Transition: Let’s look at the final phase of an ONLINE index operation. Slide Comment: Additional Information: SQL Server 2005 Books Online: Topic: “How Online Index Operations Work” Acceso de sólo escritura Exploración de datos Ordenar / Fusionar Insertar operaciones masivas SELECT UPDATE DELETE INSERT Bloqueo de IS

30 Operación en línea de indexación en clúster
Fase final Usuarios concurrentes Fuente (Tabla) Objetivo (Indice en clúster) Bloqueo Slide Title: Online Clustered Index Operation Keywords: index, indexing, online index, online indexing Key Message: Explain how ONLINE index operations work. Slide Builds: 0 Slide Script: During the final phase, all data is copied and SQL Server once again prevents access to the table for a very short period of time. This time is used to perform cleanup on temporary objects and, more importantly, to invalidate all execution plans that used the previous table structure. This is necessary so that new transactions can use the clustered index and optimize appropriately. SQL Server uses shared locks to prevent access and intent shared locks during the copy operations. Intent shared locks do not prevent read and write operations. [BUILD1] After this phase, the clustered index is built and ready for use. Slide Transition: Now let’s move on to the last section of our session. Slide Comment: Additional Information: SQL Server 2005 Books Online: Topic: “How Online Index Operations Work” No se permite ninguna actividad Se soltó la fuente Metadatos actualizados Sch-M lock Se creó un índice en clúster

31 Agenda Comprender las barreras de la disponibilidad
Recuperarse de una falla del servidor de la base de datos Recuperarse de un error del usuario o de la aplicación Vencer las limitaciones de concurrencia Comprender la duplicación de igual a igual Slide Title: Agenda: Understanding availability with peer-to-peer replication Keywords: agenda Key Message: Introduce the next agenda item. Slide Builds: 0 Slide Script: In this section, we’ll look at how you can use peer-to-peer replication to provide a hot standby of a replication publication. We will also see how it can provide fault tolerance through time partitioning. We will then examine an advantage that peer-to-peer replication has over other high-availability options, namely, load balancing. Slide Transition: First, let’s review the features of peer-to-peer replication. Slide Comment: Additional Information:

32 Replicación de igual a igual
Proporciona espera inmediata Sin límites de distancia No hay detección de conflictos Una sola tabla para toda la base de datos Cierta pérdida de datos entregados Slide Title: Peer-to-Peer Replication Keywords: peer-to-peer replication, replication Key Message: Explain the features of peer-to-peer replication. Slide Builds: 0 Slide Script: You can use peer-to-peer replication to provide a hot standby of a replication publication. Your publications can be as small as a single table or as large as an entire database. Peer-to-peer replication publications have a few restrictions that standard replication publications do not. A table can exist in only one article that is a member of a publication configured for peer-to-peer replication. Articles assigned to a peer-to-peer replication publication cannot use horizontal or vertical filtering, nor can they contain a timestamp column. Identity columns are not recommended for peer-to-peer replication articles. If you use identity columns, you will need to manage identity ranges on all replication nodes. Unlike clustering or mirroring, peer-to-peer replication has multiple read copies of the data. Read performance can therefore be improved. Update performance is the same as a single database, although all updates must still be recorded in the database and transaction log of every server. There are no realistic distance limitations. No shared hardware is required, and no communication between the replication nodes is required to commit transactions. Transactions are not guaranteed to be committed at all nodes in the case of server failure, so some committed data loss is possible. Peer-to-peer replication uses transactional replication, so the amount of data loss is likely to be small.

33 Replicación de igual a igual (Notas)
Proporciona espera inmediata Sin límites de distancia No hay detección de conflictos Una sola tabla para toda la base de datos Cierta pérdida de datos entregados Peer-to-peer replication has no automatic conflict detection like merge replication does. You must use your application to partition updates to the database. This can be done either by explicitly coding in the application to only update certain rows or by controlling which clients can connect to which servers. You can also use time limitations on your clients to avoid conflicts. Slide Transition: The next example explains the use of time restrictions to avoid conflicts and provide high availability through peer-to-peer replication. Slide Comment: Additional Information: SQL Server 2005 Books Online: Topic: “Peer-to-Peer Transactional Replication”

34 Tolerancia a fallas de igual a igual
Slide Title: Fault Tolerance with Peer-to-Peer Keywords: peer-to-peer replication, fault tolerance Key Message: Explain the example of time partitioning for peer-to-peer replication. Slide Builds: 0 Slide Script: This example uses a company that has a support infrastructure consisting of three support offices. The offices are located in Los Angeles, London, and Taipei, Taiwan. Their customer support database is replicated using peer-to-peer replication between the three offices. In the case of failure of one of the clients, the office can use and update one of the other office’s database but during normal operation have their own, local copy of the database. Each of the support offices is open eight hours with no overlapping time, so updates will be made at only one of the databases at a time. With this scenario, no conflicts should occur and even identity columns would be reasonably safe to use. Slide Transition: Now let’s return to our demo network to see this in action. Slide Comment: Additional Information: SQL Server 2005 Books Online: Topic: “Peer-to-Peer Transactional Replication” Londres Los Ángeles Taipei

35 demo Demo Usar la duplicación de igual a igual
Configurar los servidores para duplicación Crear publicaciones y suscripciones Acceder a la base de datos duplicada Slide Title: Demonstration: Using Peer-to-Peer Replication Keywords: peer-to-peer replication Key Message: demonstration Slide Builds: 0 Slide Script: In this demonstration, we will show you how to configure servers for peer-to-peer replication. Then you’ll see how to create publications and subscriptions, and finally access a replicated database. Slide Transition: This completes our session. What have we covered today? Slide Comment: Additional Information:

36 Resumen de la sesión Diseñado para estar sumamente disponible
Nuevas opciones de alta disponibilidad Otras funciones que mejoran la disponibilidad Slide Title: Summary Keywords: Key Message: summary Slide Builds: 2 Slide Script: SQL Server 2005 is designed to be highly available. Traditional availability options have been enhanced to provide better, faster, and more reliable failover that can take place over longer distances. Failover options address everything from hardware failure to human-caused failure to natural disaster. [BUILD1] New features in SQL Server 2005, such as database mirroring, provide hot standby solutions that are extremely reliable and cost-effective and that aren’t limited by distance. Features like database snapshots are flexible and can be implemented independently to provide higher availability or to augment and enhance other high-availability options. They can also be used to provide a quick fallback option for administrators who maintain databases regularly. [BUILD2] Other features, such as the new concurrency controls and ONLINE index operations, allow for better data access during normal operation, meaning that users can continue to get to their data even when SELECTs are being performed and indexes are being created. Slide Transition: To get more information on the products and technologies we have covered today, we have some online resources available that can help. Slide Comment: Additional Information:

37 Para mayores informes Visite TechNet en Siga participando en

38 Complete el curso de SQL 2005
UNO.DOS.TRES. CONTEST Complete el curso de SQL 2005

39 ¿Escuchó las noticias acerca de TechNet?
¡Software sin límites de tiempo! Soporte técnico gratuito. Los recursos más actuales a la mano. Slide Title: TechNet Subscription Keywords: TechNet, subscription, benefits Key Message: TechNet Plus has some new benefits. Slide Builds: 0 Slide Script: Many of you may be familiar with TechNet events and the TechNet Web site, but have you realized the benefits of being a TechNet Plus subscriber? A TechNet Plus subscription is the most convenient and reliable resource for IT professionals evaluating, managing, and supporting Microsoft technologies. With a TechNet Plus subscription, you can: Evaluate Microsoft software without time limits. This benefit allows you try products at your own pace and make informed decisions without worrying about the software expiring. TechNet Plus evaluation software includes the latest Microsoft operating systems, server applications, and Office products. With TechNet Plus, you can also save time resolving technical issues. TechNet Plus subscriptions include a range of support options, including the complete Microsoft Knowledge Base delivered each month on portable media, and two complimentary professional support incidents to address your technical roadblocks. TechNet Plus offers centralized access to current, authoritative technical guidance, software and support resources from Microsoft. IT professionals around the world rely on TechNet Plus to help them build their technical expertise and be successful implementing Microsoft solutions. For details, visit Slide Transition: On the subject of TechNet and support, the new TechNet support pages outline all the support options open to you. Slide Comment: Additional Information:

40 Encuentre todas estas opciones de soporte en www. microsoft
Encuentre todas estas opciones de soporte en Microsoft ofrece una serie progresiva de opciones de soporte que inician con soporte en línea gratuito y desarrollo a través de suscripción, incidentes y soporte a contratos. 1. Soporte en línea sin cargo Knowledge Base Busque en una vasta base de datos de artículos para localizar la información que necesita. Grupos de noticias Acceda a más de 20,000 grupos de noticias activos sobre calificaciones de temas. Centros de soporte a productos Obtenga respuestas a preguntas más frecuentes, además de artículos “cómo hacerlo” e instrucciones paso por paso organizadas por producto. Base de datos de ayuda de DLL Busque aquí para identificar el software que se utiliza para instalar una versión DLL específica. Centro de eventos y mensajes de error Resuelva eventos y mensajes de error rápido con explicaciones, recomendaciones y vínculos a soporte y recursos. Soporte Webcasts Sintonícese para ver presentaciones técnicas en vivo de expertos de Microsoft y tome parte en la sesión de Preguntas y Respuestas en tiempo real. Chats Converse en línea con especialistas de Microsoft o busque los archivos transcritos. Programa de grupos de usuarios Acceda a la información y soporte para informática y a otros grupos de usuarios de interés específico. Centro de recursos de seguridad de TechNet Adelántese a los riesgos de seguridad con recursos que lo mantienen actualizado, incluyendo boletines de seguridad y el servicio de notificación de Microsoft. 2. Soporte basado en Suscripción Suscripción a TechNet Suscríbase a TechNet para obtener una biblioteca personal de artículos, paquetes de servicio, Cómo funciona, kits de recursos, herramientas, utilidades y más. Su suscripción incluye actualizaciones mensuales que se entregan en CD o DVD, de manera que siempre tiene la información más reciente, directa de la fuente. Actualícese a una suscripción a TechNet Plus y agregue todo esto: 1. Software de evaluación con versión completa, incluyendo Microsoft Office System y productos de Windows Server™ System, sin restricciones de tiempo. 2. Soporte gratuito — dos incidentes gratuitos, más un descuento en otras llamadas de soporte. 3. Acceso ilimitado al día hábil siguiente a respuestas confiables de la comunidad informática y el personal de soporte de Microsoft mediante Grupos de noticias moderados (sólo inglés). 3. Soporte asistido a incidentes Soporte por correo electrónico Obtenga ayuda en línea para incidentes a través de correo electrónico de un Profesional en soporte de Microsoft. Soporte telefónico Obtenga ayuda telefónica para incidentes de un profesional de soporte de Microsoft. Contrato de soporte telefónico Ahorre con un contrato de soporte telefónico de 5 paquetes. Servicios de asesoría Agregue opciones de asesoría que ofrecen los Servicios de asesoría de Microsoft de manera remota para dar soporte proactivo que va más allá del mantenimiento de rutina a los productos. 4. Soporte basado en contratos Soporte premier Obtenga la flexibilidad de relacionar opciones de soporte con su organización y disfrute el acceso directo a los expertos técnicos de Microsoft en cualquier momento, durante el día o la noche. Soporte premier ofrece opciones personalizadas para negocios con necesidades complejas, incluyendo profesionales técnicos dedicados para supervisar su soporte, resolución de problemas las 24 horas y capacitación y talleres para mantener actualizado a su personal de informática. Soporte esencial Soporte esencial ofrece opciones empacadas específicamente diseñadas para satisfacer los requisitos de soporte fundamentales de cualquier negocio, grande o pequeño. Incluye administración de cuentas, resolución de problemas y servicios de información. Slide Title: TechNet Troubleshooting and Support Keywords: community Key Message: Where to get more help Slide Builds: 0 Slide Script: The enhanced TechNet Troubleshooting and Support page outlines all the ways to get support assistance from Microsoft. From free online support options to subscription-based support, you’ll find all your Microsoft support resources in one location at Slide Transition: TechNet also provides a number of community resources. Slide Comment: Additional Information:

41 ¿Dónde más puedo obtener ayuda?
Chats y difusiones por el Web gratuitas Lista de grupos de noticias Sitios de la comunidad de Microsoft Eventos de la comunidad y columnas Slide Title: Community Help Keywords: community Key Message: Where to get more help Slide Builds: 0 Slide Script: There are a number of free community resources available on TechNet. You can attend a regular chat with members of the products groups or technology specialists from Microsoft, or you can attend a webcast where you can see sessions like the one you’ve just watched but presented live and with the ability to ask questions as you go. You can also read or post questions in the public newsgroups. The Newsgroup page lists the available groups and provides an interface from which you can read and post messages. TechNet Plus subscribers can use these groups to post questions that, through their subscription ID, will be answered by Microsoft within 24 hours. The main community site provides a comprehensive list of resources available—more than we can cover on this slide—plus the page has some dynamic features with continually updated content. The Events page provides dates and details where you can attend a TechNet event live. These events take place worldwide and provide the opportunity for you to talk to Microsoft specialists face-to-face. And finally, the TechNet Columns provide a variety of topics written by industry authors. Slide Transition: [Thank the audience for attending and sign off.] Slide Comment: Additional Information: