BUG: Unhandled Exception in SQL Server Using Keyset Cursors

• Microsoft SQL Server, version 6.5

SYMPTOMS

SQL Server seems to stop responding and becomes unresponsive when running cursor queries that require keyset cursors. The errorlog indicates an access violation (AV) and the following error:

   closetable: table already closed for sdes '%*.d'

   Error 10037
   Unexpected EOF from SQL Server.  Connection broken.

CAUSE

SQL Server version 6.5 introduced the asynchronous generation of keysets for keyset cursors, using "subprocess." The optimizer decides the number of records in the result set based on the statistics information, and if this number is within the cursor threshold, the keyset values are generated synchronously. When this number exceeds the "cursor threshold" setting, it uses asynchronous generation of keysets by forking a "subprocess" to populate the keyset cursor. When the subprocess completes, it closes itself and while doing so, it generates an access violation that is not completely handled.

WORKAROUND

To work around this problem, either set the "cursor threshold" configuration parameter to a higher value, or set it to the default setting of -1 (all cursors will be generated synchronously). Running update statistics to have latest distribution information may help the optimizer determine the result set more accurately.

STATUS

Microsoft has confirmed this to be a problem in Microsoft SQL Server version 6.5. We are researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.

If any replication-related process runs into the above scenario, Sqlexec.exe also generates an unhandled exception error before Sqlservr.exe. Otherwise, if the SQLExecutive service is set to restart the MSSQLServer service, the service will be restarted and the client gets the following error message:

   Unexpected EOF from SQL Server. Connection Broken.