Hướng dẫn học Microsoft SQL Server 2008 part 110 pptx

Nielsen c44.tex V4 - 07/21/2009 2:34pm Page 1052 Part VI Enterprise Data Management Detaching and Attaching Though it is often overlooked, one of the easiest ways to move a database from one computer to another is to detach the database, copy the files, and attach the database to SQL Server on the destination computer. For developers who frequently move databases between notebooks and servers, this is the recommended method. Detaching a database effectively deletes the database from SQL Server’s awareness but leaves the files intact. The database must have no current connections and not be replicated if it is to be detached. Only members o f the SysAdmins fixed server role may detach and attach databases. For more details on the security roles, refer to Chapter 50, ‘‘Authorizing Securables.’’ Detaching and attaching the database will carry with it any database users, security roles, and permis- sions, but it will not replicate server logins. These will need to be resolved manually on the destination server. It’s best to coordinate security with the network administration folks and leverage their security groups. If the source and destination servers have access to the same network security groups, this will alleviate the security login issues for most installations. Using Management Studio, right-click the database to be copied and select Tasks ➪ Detach. The Detach Database dialog, shown in Figure 44-17, will appear. FIGURE 44-17 The Detach Database feature removes the database from SQL Server’s list of databases and frees the files for copying 1052 www.getcoolebook.com Nielsen c44.tex V4 - 07/21/2009 2:34pm Page 1053 Transferring Databases 44 Once the database file is detached, it will disappear from the list of databases in Management Studio. The files may be copied or moved like regular files. To reattach the database file, select Databases in the Management Studio console tree and Tasks ➪ Attach from the action menu or context menu. The Attach Databases dialog, shown in Figure 44-18, simply offers a place to select the file and verify the file locations and names. FIGURE 44-18 The database may be reattached by means of Management Studio’s Attach Databases tool In code, the database is detached by running the sp_detach_db system stored procedure. The first parameter is the database to be detached. A second optional parameter simply turns off automatic updating of the index statistics. The following command detaches the AdventureWorks2008 sample database: sp_detach_db ‘AdventureWorks2008’ If you wish to reattach a database with code, the counterpart to sp_detach_db is the sp_attach_db system stored procedure. Attaching a database requires specifying the file locations as well as the database name, as follows: EXEC sp_attach_db @dbname = ‘AdventureWorks2008’, @filename1 = ‘ G:\MSSQL10.INST1\MSSQL\Data\AdventureWorks2008_ Data.mdf’, @filename2 = ‘H:\MSSQL10.INST1\MSSQL\LOG\AdventureWorks2008_Log.ldf’ 1053 www.getcoolebook.com Nielsen c44.tex V4 - 07/21/2009 2:34pm Page 1054 Part VI Enterprise Data Management Best Practice I t is recommended to use CREATE DATABASE database_name FOR ATTACH instead of the sp_attach_db stored procedure, as it will be removed in a future version of SQL Server. Here is an example: CREATE DATABASE AdventureWorks2008 ON (FILENAME = ‘ G:\MSSQL10.INST1\MSSQL\Data\AdventureWorks2008_Data.mdf’), (FILENAME = ‘H:\MSSQL10.INST1\MSSQL\LOG\AdventureWorks2008_Log.ldf’) FOR ATTACH; Special Instructions for Detaching and Attaching the msdb and model Databases D etaching and attaching the msdb and model databases results in an error by default. In order to detach and attach the msdb and model databases, you need to start SQL Server with the -c option, the -m option, and trace flag 3608. Trace flag 3608 recovers only the master database. Once you start SQL Server with these startup parameters, you can detach/attach msdb and model databases without any error message. Import and Export Wizard On many occasions SQL DBAs need to do the following: ■ Copy only a few tables from one SQL Server database to another SQL Server database ■ Import data from a flat file or Microsoft Office Excel file ■ Copy data from one table to another with different collations To achieve these DBA tasks easily and quickly, Microsoft has provided another powerful wizard called SQL Server Import and Export Wizard. This wizard enables copying data to and from any data source for which a managed .NET Framework data provider or a native OLE DB provider i s available. You can access the Import and Export Wizard from various locations: ■ Choose Import and Export Data from Start ➪ Programs ➪ Microsoft SQL Server 2008. ■ Open Management Studio, right-click a database and choose Task ➪ Import Data or Export Data from the context menu 1054 www.getcoolebook.com Nielsen c44.tex V4 - 07/21/2009 2:34pm Page 1055 Transferring Databases 44 ■ Open SQL Server Business Intelligence Development Studio ( BIDS) from Start ➪ Programs ➪ Microsoft SQL Server 2008. Open an SSIS solution, select SSIS Import and Export Wizard f rom the Project menu or by right-clicking the SSIS Packages folder. ■ Run DTSWizard.exe (C:\Program Files\Microsoft SQL Server\100\DTS\Binn) from the command prompt. To move data with the Import and Export Wizard, follow these steps: 1. Launch the Import and Export Wizard using one of the preceding methods. 2. Skip past the Welcome to SQL Server Import and Export Wizard by clicking Next. 3. On the Choose a Data Source page, select the source data. If you launched the wizard from Management Studio by right-clicking the database and choosing Task ➪Export Data, the source information is already preconfigured with the server and database name. Depending on the source data, the other options on this page will vary. For example, selecting SQL Server Native Client 10.0 allows you to specify the SQL Server, a uthentication, and database, as shown in Figure 44-19. Click Next to proceed. FIGURE 44-19 Selecting SQL Server Native Client 10.0 as the data source and the AdventureWorks database 4. On the Choose a Destination page, select the destination target. If you launched the wizard from Management Studio by right-clicking the database and choosing Task ➪Import Data, 1055 www.getcoolebook.com Nielsen c44.tex V4 - 07/21/2009 2:34pm Page 1056 Part VI Enterprise Data Management the destination information is already preconfigured with the server and database name. This page also allows you to create a new destination database by clicking the New option, which invokes the dialog shown in Figure 44-20. FIGURE 44-20 Clicking New enables you to create a destination database 5. The Specify Table or Query page enables you to either copy all the data from existing source tables or views or write a T-SQL query to limit the data to copy. 6. On the Select Source Tables and Views page, select all the tables and views you want to copy. If you opted to write a query on the previous page, then you can just select the query on this page. Click Preview to preview up to 200 rows of source data. Click Edit Map- pings to change the destination column names, data types, nullability, and size, as shown in Figure 44-21. If the destination table exists, you can either delete or append rows to it. If there is no destination table, you can create one. 7. Depending on how you launched the Import and Export Wizard, the last step varies. For example, if you launched the wizard from BIDS, then in the last step you cannot run the resulting package; instead the package is saved as part of the SSIS solution. If you launched the wizard from any other method (for example, Management Studio), then the wizard allows running the package in the last step, as shown in Figure 44-22. Best Practice T o copy the full database or multiple databases, use the Copy Database Wizard instead of the Import and Export Wizard. 1056 www.getcoolebook.com Nielsen c44.tex V4 - 07/21/2009 2:34pm Page 1057 Transferring Databases 44 FIGURE 44-21 Configuring the destination table and column mappings FIGURE 44-22 Running the package immediately and saving the package with encryption 1057 www.getcoolebook.com Nielsen c44.tex V4 - 07/21/2009 2:34pm Page 1058 Part VI Enterprise Data Management Summary When you need to move a database, don’t back it up; there are better ways to move it. Choose the right transfer method based on network proximity of the servers and the objects and/or data to be moved. Some key points to remember are as follows: ■ Use the Detach/Attach method to quickly and easily move or copy a database from one server to another. ■ If you cannot afford to detach a database, use the good old Backup/Restore method to copy a database from one server to another. ■ The Copy Database Wizard is very useful for copying or moving one or more databases from one server to another on the same network. ■ To copy only a few tables from one server to another or to copy data to and from any data source for which a managed .NET Framework data provider or a native OLE DB provider is available, use the Import and Export Wizard. ■ Use Management Studio to quickly generate scripts to distribute database schemas, security, jobs, and limited data. Chapter 41, ‘‘Recovery Planning,’’ covers not only techniques for performing a backup, but also working with transaction logs and recovering various data objects, up to an entire server. 1058 www.getcoolebook.com Nielsen c45.tex V4 - 07/21/2009 3:15pm Page 1059 Database Snapshots IN THIS CHAPTER How database snapshots work Creating a database snapshot Using your database snapshots Performance considerations and best practices T he Database Snapshot feature, originally introduced in SQL Server 2005, allows for a point-in-time, read-only, consistent view of your user databases to use for reporting, auditing, or recovering purposes. Before database snapshots, this functionality was achieved by running a backup and restoring it to another database. The big advantages provided by database snapshots are the speed at which they can be created, as well as the ability to create multiple database snapshots of the same source database, providing you with snapshots of the database at different times. The Database Snapshot feature is only available in Enter- prise and Developer Editions of SQL Server 2008. The Database Snapshot feature was primarily designed to do the following: ■ Generate reports without blocking the production/source database. ■ Perform reporting on a database mirror. ■ Recover from user or administrator errors. ■ Revert the source database to an earlier time. ■ Manage a test database. Database snapshots are similar to databases in many ways but they do have some limitations of which you should be aware: ■ Database snapshots are read-only static copies of the source database. ■ Database snapshots cannot be created for system databases ( master, model,andtempdb). ■ Database snapshots can be created only on an NTFS file system. 1059 www.getcoolebook.com Nielsen c45.tex V4 - 07/21/2009 3:15pm Page 1060 Part VI Enterprise Data Management ■ Database snapshots can be created only on the same SQL Server instance where the source database exists. ■ Database snapshots depend on the source database, so if the source database is unavailable f or any reason, then all its database snapshots will become unavailable too. ■ The source database cannot be dropped, detached, or restored as long as it has any database snapshots; but source database backups are not affected by database snapshots. ■ You cannot backup or restore a database snapshot. Nor can you attach or detach a database snapshot. ■ You cannot revert to the database snapshot if you have multiple database snapshots. You will need to drop all the database snapshots except the one to which you want to revert. ■ Database snapshots do not support Filestream. ■ Full-text indexing is not supported on database snapshots, and full-text catalogs are not propagated from the source database. ■ In a log shipping configuration, database snapshots are allowed only on the primary database, not on the secondary or warm-standby database. ■ Database snapshots are I/O intensive and may impact the performance of the system. If these limitations are acceptable, then Database Snapshots can be an excellent feature that you can use to create point-in-time, read-only copies of your production databases. How Database Snapshots Work As discussed earlier, a database snapshot is a point-in-time, read-only, static vi ew of the source database as it existed at the time the database snapshot was created. When a database snapshot is created, SQL Server runs recovery on the database snapshot and rolls back uncommitted transactions to make the database snapshot transactionally consistent. The transactions in the source database are not affected. A database snapshot is not the same as the source database. It is a different database that has the same number of data files as the source database but it does not have any transaction log file. When it is initially created, the data files in the snapshot database do not contain any user data and are almost empty. That is why creating a database snapshot does not take a long time. Database snapshots use a copy-on-first-write method for each source database page that is updated for the first time after the database snapshot is created. For every database snapshot, SQL Server creates an in-memory bitmap. It has a bit for each data page indicating if the page is copied to the snapshot. Every time an update is made to the source database, SQL Server checks the bitmap to see if it has been copied to the snapshot. If it is not copied, then SQL Server copies the data page from the source database to the database snapshot and then makes the update. Next time, if the same page is updated, it is not copied, as the database snapshot just contains the data as it existed on the source database when the snapshot was created. This is referred to as copy-on-first-write technology and is shown in Figure 45-1. If a data page on the source database is never updated, it is never copied to the database snapshot. 1060 www.getcoolebook.com Nielsen c45.tex V4 - 07/21/2009 3:15pm Page 1061 Database Snapshots 45 FIGURE 45-1 Database snapshot using copy-on-first-write technology Data Page Data Page Source Database Database Snapshot Data Page at the time snapshot was created Updated Data Page Unallocated Page Update Creating a Database Snapshot Database snapshots can be only created using the Transact-SQL CREATE DATABASE AS SNAPSHOT command. SQL Server Management Studio does not have any graphical interface to create database snapshots. Here are the step-by-step instructions to create a database snapshot of the AdventureWorks sample database: 1. The first step is to find out the information about the files in the source database. The follow- ing command can be used to retrieve information about the files in the AdventureWorks database: USE AdventureWorks; GO EXECUTE sp_helpfile; GO Result (abridged): name filename size AdventureWorks_Data G:\ \AdventureWorks_Data.mdf 200640KB AdventureWorks_Log H:\ \AdventureWorks_Log.ldf 504KB 1061 www.getcoolebook.com . version of SQL Server. Here is an example: CREATE DATABASE AdventureWorks2008 ON (FILENAME = ‘ G:MSSQL10.INST1MSSQLDataAdventureWorks2008_Data.mdf’), (FILENAME = ‘H:MSSQL10.INST1MSSQLLOGAdventureWorks2008_Log.ldf’) FOR. sp_attach_db @dbname = ‘AdventureWorks2008’, @filename1 = ‘ G:MSSQL10.INST1MSSQLDataAdventureWorks2008_ Data.mdf’, @filename2 = ‘H:MSSQL10.INST1MSSQLLOGAdventureWorks2008_Log.ldf’ 1053 www.getcoolebook.com Nielsen. Wizard On many occasions SQL DBAs need to do the following: ■ Copy only a few tables from one SQL Server database to another SQL Server database ■ Import data from a flat file or Microsoft Office Excel