TempDB is a critical system databases that has been available with SQL Server for ages. It is critical for performance because it is a shared database for the whole instance. Not only is it capable of alloweing users create temporary tables, but it is also used internally by SQL Server to perform hashing, sorting, and reindexing. It can also keep the version store to support various isolation levels. But it is also a database that needs considerable tuning from an administrator’s point of view when working in production environments. There is no one-size-fits-all with TempDB.
The Microsoft product support team has continued to add enhancements to the TempDB database. If you have worked with SQL server performance optimization, you might recall trace flags # 1117 and 1118. These are documented by Microsoft under knowledge base article 328551, Concurrency Enhancements for the TempDB Database. I highly suggest you look at the KB article mentioned above to further inform your understanding. Or take the easier road and simply move to SQL Server 2016.
Here are some quick tests on SQL Server 2016 along with its predecessor, SQL Server 2014 that demonstrate the benefits of new enhancements.
SQL Server 2016 Does Not Require Trace Flag 1117
To test it, we have created four TempDB data files in both SQL Server versions, each 8 MB. This is how it looks on both SQL instances.
< Now, we have run the following script to create a large table in TempDB. Our goal is to grow the TempDB database files.
CREATETABLE #tempdbtable(i int,j char(8000)) GO INSERTINTO #tempdbtable VALUES (1,’SOME DATA’) GO 10000
The above script would create a wide temporary table in the TempDB database and insert about 10K rows. Since the initial size of TempDB is not sufficient, it will cause the file to grow. If we look at the TempDB file after the script execution, we can see the size difference.
SQL Server 2016 Does Not Require Trace Flag 1118
Microsoft SQL Server 2016 doesn’t need these trace flags because their behavior is already enabled by default. Along with the trace flag, the SQL Server 2016 setup also has a TempDB configuration screen during installation. This is how it looks:
The settings are under a tab called “TempDB” on the “Database Engine Configuration” page. This screen automatically picks up the number of CPUs on the machine and provides the number of files needed. The size, growth, and number of files can be adjusted during the installation itself. This is going to remove one of an additional “post-install-scripts” steps which big companies generally follow.
In short, SQL Server 2016 delivers improvements to make TempDB more scalable out of the box. There is no need to add more files, size them, or add trace flags.
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