Schema Modification Locks With CC Compliance

Lori Brown explains why you might see schema modification locks after enabling Common Criteria compliance:

We have a client who has no idea how or when Common Criteria was enabled on their production system. All they know is that performance has been slowly degrading. After collecting performance data, we found that there were high LCK_M_SCH_M waits which is a schema modification lock that prevents access to a table while a DDL operation occurs. We also found blocked process records where a LOGIN_STATS table in the master database was waiting a lot. This table is used to hold login statistics. When there are a lot of logins and outs there can be contention in this table.

When you enable Common Criteria compliance, something called Residual Information Protection (RIP) is enabled. RIP is an additional security measure for memory and it makes it so that in memory a specific bit pattern must be present before memory can be reallocated(overwritten) to a new resource or login. So with lots of logins and outs, there is a performance hit in memory because overwriting the memory allocation has to be done.

It’s worth reading the whole thing.

Related Posts

Safely Dropping Databases

Bob Pusateri notes a little issue when it comes to dropping databases: At a previous employer, we had a well-defined process when dropping databases for a client. It went something like this: Confirm in writing the databases on which servers/instances to be dropped Take a final full backup of databases Take databases offline Wait at […]

Read More

New DMF: dm_db_page_info

Pam Lahoud shows off a new Dynamic Management Function in SQL Server 2019: The primary use case we had in mind when developing this function was troubleshooting page-related waits. Some of the key performance scenarios that require page details to diagnose are tempdb contention, last page insert contention (also see this blog articlefor code samples) and page-level blocking. All of […]

Read More

Categories