Microsoft KB Archive/164215

= FIX: Bad Token or AV If Sp_cursoropen After Dropping Index =

Article ID: 164215

Article Last Modified on 8/10/2006

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APPLIES TO


 * Microsoft SQL Server 6.5 Standard Edition

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This article was previously published under Q164215



BUG #: 16556 (6.5)



SYMPTOMS
Sp_cursoropen generates an access violation (AV) in xpcursordeclare (on a checked server) or breaks the connection (on a retail server) if you do all of the following:


 * 1) Open an extended KEYSET_DRIVEN or INSENSITIVE extended cursor on a stored procedure that references a table containing a unique clustered index, non-clustered index, or primary key (PK) constraint.
 * 2) Close the cursor.
 * 3) Drop the index or constraint.
 * 4) Open the cursor again.

The symptom of the broken connection is usually a "bad token" message returned to the client. Slight variations of this may cause an AV in cursornewrow on a checked (or debug) server.

An extended KEYSET_DRIVEN cursor is exposed at the DB-Library API layer as CUR_KEYSET in dbcursoropen and at the ODBC API layer as SQL_CURSOR_KEYSET_DRIVEN in SQLSetStmtOption. An extended INSENSITIVE cursor is exposed at the DB-Library layer as CUR_INSENSITIVE in dbcursoropen, and at the ODBC API layer as SQL_CURSOR_STATIC in SQLSetStmtOption.



WORKAROUND
To work around this problem, do any of the following:


 * Use a different cursor type.
 * Use trace flag -T7502 to "Disable caching cursor plans in procedure cache."
 * Create the stored procedure WITH RECOMPILE.
 * Drop and re-create the stored procedure after making a table schema change.



STATUS
Microsoft has confirmed this to be a problem in Microsoft SQL Server version 6.5. This problem has been corrected in U.S. Service Pack 3 for Microsoft SQL Server version 6.5. For more information, contact your primary support provider.



MORE INFORMATION
SQL Server supports two different server-side cursor interfaces. One is ANSI SQL cursors, which are exposed through Transact-SQL statements such as DECLARE, FETCH, and so on. The other cursor interface is an extended cursor interface that is accessed through the DB-Library and ODBC APIs. The sp_cursor extended cursor statements are emitted by the DB-Library or ODBC layers in response to certain DB-Library or ODBC API calls. Higher- level interfaces such as Remote Data Objects (RDO) will often encapsulate these API-level calls, so you would need to run a trace utility such as SQL Trace to verify the sp_cursor call being made.

Keywords: kb3rdparty kbbug kbfix kbhardware KB164215

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