Mystery of Identity Column Value Jumps in SQL Server
Encountering sudden jumps in identity column values to 1001 in SQL Server 2012 can be disconcerting. To understand this phenomenon, it's essential to delve into Microsoft's modified handling of identity values in this version.
In SQL Server 2012, identity generation is designed to be more efficient and resilient. However, this introduces some potential gaps between identity values. These gaps can arise due to server restarts or updates, which can cause a "reset" of the identity value counter.
To mitigate this issue, SQL Server 2012 offers two options:
-
Using Trace Flag 272:
- Activating Trace Flag 272 logs each generated identity value. While this provides visibility into the identity generation process, it may impact performance.
-
Implementing a Sequence Generator with NO CACHE Setting:
- Create a sequence generator and set the NO CACHE property. This ensures that identity values are not cached, preventing gaps.
Setting Trace Flag 272:
- Launch SQL Server Configuration Manager.
- Select "SQL Server Services" and right-click on the SQL Server instance.
- Choose "Properties."
- Navigate to "Startup Parameters."
- Enter "-T272" in the "Specify a startup parameter" field.
- Add and confirm the change.
By utilizing these options, developers can manage identity column values effectively, avoiding the confusion caused by sudden jumps.
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