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Title
SQL Optimization 'Optimize SQL by Plan Control' error: Access violation at address 21505426 in module 'QOptEngineLib.dll'. -
Description
SQL Optimization 'Optimize SQL by Plan Control' error:
"Access violation at address 21505426 in module 'QOptEngineLib.dll'. Read of address 00000004"
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Cause
Optimization was being done on a read-only database. -
Resolution
Since it needs to deploy alternative plan to SQL Server during the optimizing plan process, try not to do this on read-only databases. It is also better that the login has sysadmin role. Also, because the Plan Control is to deploy plan guide to improve the performance, some limitations about Plan Guides should be aware of such as the query text should be exactly matched.