Identity column value suddenly jumps to 1001 in sql server

I believe you have the explanation in a comment to this connect item. Failover or Restart Results in Reseed of Identity

To boost the preformance for high end machines, we introduce preallocation for identity value in 2012. And this feature can be disabled by using TF 272 (then you will get the behaviour from 2008R2).

The identity properties are stored separately in metadata. If a value is used in identity and increment is called, then the new seed value will be set. No operation, including Rollback, Failover, ..... can change the seed value except DBCC reseed. Failover applies for the table object, but no the identity object. So for failover, you can call checkpoint before manual failover, but you may see gap for unplanned cases. If gap is a concern, then I suggest you to use TF 272.

For control manager shutdown, we have a fix for next verion (with another TF). This fix will take care of most control manager shutdown cases.

I guess you could use sequence instead, sequence gives you 100% complete control, and is in many ways far superior in comparison to identity... Identity is just so damn easy and convenient

http://msdn.microsoft.com/en-us/library/ff878091.aspx

As far as i know, when you do a insert with identity and fails, the identity is used anyway, Verified

with sequence you can make it "fill" gaps using cycle. Although, as Amy Barrett is pointing out this is created out of scope of the transaction.

There is a performance optimization when you are using cache that might be useful as well.

Microsoft has changed the way they deal with identity values in SQL Server 2012 and as a result of this you can see identity gaps between your records after rebooting your SQL server instance or your server machine. There might be some other reasons for this id gaps, it may be due to automatic server restart after installing an update.

You can use below two choices

• Use trace flag 272 o This will cause a log record to be generated for each generated identity value. The performance of identity generation may be impacted by turning on this trace flag.

• Use a sequence generator with the NO CACHE setting

  Setting Trace Flag 272 on SQL Server 2012 that you are expecting here

• Open "SQL Server Configuration Manager"

• Click "SQL Server Services" on the left pane

• Right-click on your SQL Server instance name on the right pane ->Default: SQL Server(MSSQLSERVER)

• Click "Properties"

• Click "Startup Parameters"

• On the "specify a startup parameter" textbox type "-T272"

• Click "Add"

• Confirm the changes