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MEMORY MANAGEMENT - WORKING SET TRIMMING
Description: Working Set Trimming refers to a condition wherein all Working Sets are flushed to the disk. A Working Set is the amount of physical memory used by a process. Working Set Trimming is primarily seen on SQL Server systems when large amounts of physical memory are allocated to the SQL Server processes and a new request for resource allocations is made that exceeds the amount of free available resources. In order to satisfy the new allocation request the Working Set manager flushes all the Working Sets for all the processes to disk (not just the SQL ones). Only the bare minimum needed to run these processes remains allocated.
Scoping the Issue: Although we normally see Working Set Trimming Issues on SQL Servers (SQL Server 2000 and later), we have also seen the issue surface on other application servers that make use of large databases – for example, Microsoft Exchange 2007 servers and Microsoft Data Protection Manager (DPM) Servers. Let’s take a look at each of these scenarios in turn:
Microsoft SQL Servers: Based on the version of SQL Server in use, and the configuration, there are a combination of symptoms that you may experience.
Microsoft Exchange Server 2007: In the event that Exchange 2007 servers experience a Working Set flush, common symptoms include the following:
Microsoft Data Protection Manager (DPM): DPM servers experience the same symptoms as described above for Microsoft SQL Servers. DPM servers will also experience failures when trying to take snapshots.
In each of the application server scenarios outlined above, the server will eventually recover as the running processes reacquires resources it was previously using. However, this may take anywhere from minutes to hours, depending on the amount of physical RAM and the processing taking place on the system.
Data Gathering: In all instances, collecting either MPS Reports with the General, Internet and Networking, Business Networks and Server Components diagnostics, or a Performance-oriented MSDT manifest must be done. Additional data required may include the following:
Troubleshooting / Resolution: After you have gathered this data, review the following: