Question: How does the procedure
dbms_shared_pool.markhot work?
Answer: The
dbms_shared_pool.markhot procedure is new in 11g r2 and
marks a library cache object as a "hot" object in an attempt
to reduce "mutex contention" wait events in Oracle 11g r2
and beyind.
There is also dbms_shared_pool.unmarkhot
procedure to unmark the hot object in the library cache.
See MOSC Note 727400.1 titled "WAITEVENT:
"library cache: mutex X" for additional details on using
the markhot and unmarkhot procedures.
Here is an example of using the dbms_shared_pool markhot
procedure. This is ud in a database startup trigger,
just like
dbms_shared_pool_keep.
exec
dbms_shared_pool.markhot('SYS','DBMS_APPLICATION_INFO',1);
Oracle guru Andrey S. Nikolaev notes that
dbms_shared_pool.markhot is related to a hidden
parameter _kgl_hot_object_copies:
By default, Oracle created approximately
"number of CPU Cores" hot objects copies. This observation
should be further investigated.
You can adjust this number by
_kgl_hot_object_copies parameter. Therefore if you prefer
not to use hidden parameters, the dbms_shared_pool.markhot()
can help you to resolve mutex contention.
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