Details: Reorganize Index HAWAII Reorganize index on Local server connection Databases: AdventureWorks Object: Tables and views Compact large objects Task start: 2009-07-30T15:05:51.. [A
Trang 1After the Reorganize Task runs, it produces a text report similar to the following:
Microsoft(R) Server Maintenance Utility (Unicode) Version
10.0.2531
Report was generated on "HAWAII."
Maintenance Plan: MaintenancePlan
Duration: 00:00:15
Status: Succeeded.
Details:
Reorganize Index (HAWAII)
Reorganize index on Local server connection
Databases: AdventureWorks
Object: Tables and views
Compact large objects
Task start: 2009-07-30T15:05:51.
Task end: 2009-07-30T15:06:06.
Success
Command:USE [AdventureWorks]
GO
ALTER INDEX [PK_AWBuildVersion_SystemInformationID] ON [dbo] [AWBuildVersion] REORGANIZE WITH ( LOB_COMPACTION = ON )
GO
USE [AdventureWorks]
GO
ALTER INDEX [PK_DatabaseLog_DatabaseLogID] ON [dbo].[DatabaseLog] REORGANIZE WITH ( LOB_COMPACTION = ON )
GO
While the above is an abbreviated report, yours will show the ALTER INDEX command run for every index in every table in your selected databases If there are any problems or error messages, you will see them here also
Reorganize Versus Rebuild
Trang 2Reorganize Index Task Rebuild Index Task Removing
empty space
and logical
fragmentation
Performs a less thorough index defragmentation than Rebuild Index
If an index does not have any fragmentation, then it is not reorganized, saving resources
Virtually all wasted free space and logical fragmentation is removed All indexes are rebuilt from scratch, whether they need it
or not
Performance
impact
Does not require long blocking locks
An online task that allows users
to access the database during the task
Requires potentially long blocking locks that prevent users from accessing the indexes being rebuilt
A task that should be performed offline, though with the Enter-prise Edition of SQL Server, you can use the online version of rebuilding
an index
Speed Generally takes longer to run than
the Rebuild Index Task
Generally runs faster than the Reorganize Index Task
Space
requirements Uses less disk space than the
Rebuild Index Task
Uses less space in the transaction log than the Rebuild Index Task
Uses more disk space than the Reorganize Index Task
More space is required in the transaction log than the Reorgan-ize Index task
Statistics
maintenance Index and column statistics must
be updated separately This adds
to the administration hassle
Index and column statistics are automatically updated as part of this step, using the FULLSCAN option
Trang 3When and How Often to Reorganize Indexes
As I stated in the previous chapter, my general preference is to use the Rebuild Index task, as long as it fits into my available maintenance window If I don't have an available maintenance window, then I generally use the Reorganize Index task, along with the Update Statistics task So, before you choose Reorganize over Rebuild, or vice versa, you need to determine what your maintenance windows are
While the Reorganize Index task does offer you the option to run the task outside
maintenance windows, I would still advise against this if possible Although the performance impact of this task, along with Update Statistics, will be much lower than for the
Rebuild Index task, it could still be felt by the users, especially if your database tables are large and your servers busy
As such, if you've chosen the Reorganize Index task, here are my general scheduling recommendations, when using the Maintenance Plan Wizard
• Nightly, if possible If running both the Reorganize Index task and Update
Statistics task does not significantly affect users, I suggest you run these two tasks daily, picking a time when running them will have the least impact
• Consider alternatives, otherwise If running the Reorganize Index task and Update Statistics task does affect user performance, then you may need to consider exerting
a finer-grained control over the process, using T-SQL or PowerShell scripts
Configuring the Reorganize Index Task
Trang 4Figure 8.1: The Reorganize Index Task screen is similar to the Rebuild Index Task, but it
has fewer options.
Database Selection
The options here, with the Databases, Object and Selection drop-down boxes, are the same
as those described in the equivalent section of the Rebuild Index chapter (Chapter 7), so I will not walk through them again
As before, my advice is that you select the same database or databases here as for every other
Trang 5Don't be tempted to configure Rebuild and Reorganize in a single plan
While it is possible to create a single Maintenance Plan that will run the Reorganize
Index task and the Update Statistics task for some databases, and to run the
Rebuild Index task for other databases, this can get confusing very quickly Instead,
create separate Maintenance Plans, as I described previously.
As with the Rebuild Index task, you also have the ability to select an individual database, and then narrow the scope of the task to one or more tables or indexed views Just as I suggested you should not use this feature with the Rebuild Index task, I make the same recommendation here If you are at the point where you need to pick and choose which tables and indexed views to reorganize, then you would be better off using T-SQL or PowerShell scripts to do this task for you, as the Maintenance Plan Wizard is very inflexible
Compact large objects
The only major task-specific option that we need to consider is whether or not to select the
Compact large objects option, as shown in Figure 8.2.
Figure 8.2: Generally, you will want to keep this option selected.
It is checked by default, which means that if a table on which this task runs stores LOB data (text, ntext, or image data types), then LOB data in these tables will be treated just the same
as any other type of data, and will be reorganized
If you deselect this option, then LOB data will not be reorganized Generally, you will want
to keep this option selected, as reorganizing LOB data can boost the performance of your
LOB data, then this task will take more time, which is