Microsoft KB Archive/196919

= FIX: Descending Index Scans May Block with High Transaction Isolation =

Article ID: 196919

Article Last Modified on 3/14/2006

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APPLIES TO


 * Microsoft SQL Server 7.0 Standard Edition

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This article was previously published under Q196919



BUG #: 52498



SYMPTOMS
A descending index scan with a SERIALIZABLE transaction isolation level or a HOLDLOCK hint can hold a lock that prevents inserts greater than the highest value current in the table for the index the scan is performed on.



WORKAROUND
To work around this problem, do not use descending index scans when using a SERIALIZABLE transaction isolation level or a HOLDLOCK hint.



STATUS
Microsoft has confirmed this to be a problem in SQL Server 7.0. This problem has been corrected in U.S. Service Pack 1 for Microsoft SQL Server 7.0. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

232570INF: How to Obtain Service Pack 1 for Microsoft SQL Server 7.0 and Microsoft Data Engine (MSDE) 1.0

For more information, contact your primary support provider.



MORE INFORMATION
The following example queries clarify this problem:

--query 1:

create table t(x int primary key) insert into t values(0) insert into t values(2) insert into t values(3) insert into t values(4) insert into t values(6) go  set transaction isolation level serializable begin transaction go  select * from t where x < 3 order by x desc go

--query 2: Run from another connection

insert into t values(1) -- blocked as expected go

--query 3: Run from another connection

insert into t values(5) -- works go  insert into t values(7) -- blocked until query 1 client releases locks go

The following is the problem lock as reported by the sp_lock stored procedure:

 spid  dbid   ObjId       IndId  Type Resource         Mode     Status -- -- --- --   --

7     5      1365579903  1      KEY  (ffffffffffff)   IS-S     GRANT

Additional query words: sp_lock block serializable holdlock

Keywords: kbbug kbfix kbsqlserv700sp1fix KB196919

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