DBWR and the Shared Pool

Recently, a colleague of mine, over another discussion on performance tuning in Oracle databases mentioned that he came across an interesting note from Oracle’s Data Concurrency and Consistency Concepts guide. And here is how it reads:
“Typically, a single latch protects multiple objects in the SGA. For example, background processes such as DBW and LGWR allocate memory from the shared pool to create data structures. To allocate this memory, these processes use a shared pool latch that serializes access to prevent two processes from trying to inspect or modify the shared pool simultaneously.“. Interesting, isn’t it?

The highlighted sentence is what made me curious about it. I have some ideas (which for now may be wrong) why the DBW or LGWR may want to access the shared pool. Perhaps, some wait events are associated with it too. Need to check that as well. In the next post, I’ll try to reproduce it and come up with symptoms and solutions. I believe, it is going to be a valuable troubleshooting scenario. To be continued…

Posted in Oracle.

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