Question: I want to b able to detect
when my database gets AMM resize operations and use scripts
with see the extent of the RAM shifting then I an using AMM
See these important scripts for
detecting AMM resize
There are several views that detect
AMM resize operations.
exterminate wait event is caused when using
Oracle's "automatic memory management" (AMM) when the MMON
process shrinks the data buffer cache to re-allocate that
RAM for another SGA region. AMM resize operations can hurt
overall database performance especially the OLTP
environments, and you may want to consider turning off AMM
which will relieve the buffer exterminate waits, and
manually adjust your SGA regions.
If you suspect AMM
resize operations, you have to look into
v$sga_resize_ops and v$memory_resize_ops and
see how many times it is occurring and effecting the
performance of your database. If one sees more events of
these and especially during your peak times of database one
has to turn of the feature adjusting manually the
corresponding SGA and PGA sizes.
If you want to
analyze Oracle's use of memory and look at various memory
resizing operations you can use the
view. This view contains a list of the last 800 SGA resize
requests handled by Oracle. Here is an example:
initial_size > = 0
final_size > = 0
Please find below
the various tables that are related to AMM and their
descriptions to check the information in the database.
- displays information on the current size of all
automatically tuned and static memory components, with the
last operation (for example, grow or shrink) that occurred
displays the current sizes of all SGA components, and the
last operation for each component.
v$sga_dynamic_free_memory -- displays information
about the amount of SGA memory available for future dynamic
SGA resize operations. See my notes on
v$memory_current_resize_ops -- displays information
about resize operations that are currently in progress. a
resize operation is an enlargement or reduction of the SGA,
the instance PGA, or a dynamic SGA component.
v$sga_current_resize_ops -- displays
information about dynamic SGA component resize operations
that are currently in progress.
v$memory_resize_ops -- displays information about
the last 800 completed memory component resize operations,
including automatic grow and shrink operations for
sga_target and pga_aggregate_target.
Also see these important notes on
v$sga_resize_ops -- Displays information about the
last 800 completed SGA component resize operations.
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