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POProblems with deadlocks in recursive maintenance task
 

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  1. POProblems with deadlocks in recursive maintenance task
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    <p>I am having a problem and I want to ask some opinions on the best approach to accomplish this task.</p> <p>The process that I am implementing is a purge solution for big databases. The tables can have a variable amount of rows that can go from a few thousands to big millions. What the process will do is to delete just the data for a specific year. Partitioning is not an option here.</p> <p>I have a some initial key tables that were chosen to start the process, and from these tables I will recursively delete data, using some stored procedures built for this purpose (in order to maintain data integrity and delete only the necessary data).</p> <p>I am using SSIS to be able to start the data deletion in multiple tables at the same time but I am having problems with locks.</p> <p>The deletion process as the following steps:</p> <ol> <li>Drop all indexes on table</li> <li>Delete data in batches</li> <li>Rebuild the primary key indexes (this needs to be done for performance, because there are table with some primary keys non clustered)</li> </ol> <p>I have tried:</p> <ol> <li>Using transactions and named transactions (still have locks)</li> <li>Using sp_getapplock (still have locks)</li> </ol> <p>In SSIS I have serializable as the default isolation for the transactions.</p> <p>My main question is, because I have to do some DML and DDL in the same transaction, and this will take some time to execute, I want all tasks that need to obtain a certain lock to be waiting until the lock is released and not be targeted as deadlock victim (very the same as a mutex). </p> <p>The database will have no activity during this operation, only this process will be executed.</p> <p>This is the code I use to delete the data, and here is where the deadlocks are coming from.</p> <pre><code>select @query = N' BEGIN TRANSACTION; DECLARE @result int; EXEC @result = sp_getapplock @Resource = ''[dbo].'+@dep_tbl_nm+''', @LockMode = ''Exclusive'', @LockOwner = ''Session'', @LockTimeout = -1; EXEC CreateIndexes ''dbo.'+@dep_tbl_nm+''' EXEC CreateCoveringIndexes '''+@tbl_nm+''','''+@dep_tbl_nm+''','''+@dep_tmp_tbl_nm+''' WHILE(1=1) BEGIN DELETE TOP(50000) FROM a OUTPUT deleted.* into '+@dep_tmp_tbl_nm+' FROM dbo.'+ @dep_tbl_nm + ' AS A INNER JOIN '+@tmp_tbl_nm+' AS B ON ' + @on_list +' if(@@ROWCOUNT = 0) break; END exec (''ALTER INDEX ALL ON '+@dep_tbl_nm+' REBUILD WITH (FILLFACTOR = 80)'') COMMIT TRANSACTION;' print(@query) exec(@query) </code></pre> <p>Comments are welcome</p> <p>Regards</p>
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    1. PTQuestion
    1. USj0N45
    1. USj0N45
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      1. POProblems with deadlocks in recursive maintenance task
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      1. VTUpMod
    1. COIt could help to see the deadlock trace. [Trace Flag 1222](http://www.mssqltips.com/sqlservertip/2130/finding-sql-server-deadlocks-using-trace-flag-1222/)
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      1. USSteffe
 

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