Applying such change would require exclusive lock on the table. Maybe it cannot be obtained because some other connection uses the table?

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>I am using SSMS to change a field in a table to an identity field. However, when I try to save the change it times out (I have set the timeout to 300 seconds, but that hasn't helped).
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>This is the error:
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>Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding.
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>This is the table definition:
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<snip>

>There are only 1445 records in the table. Any ideas why this change times out?
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