Re: Partitionining perfortmance degraded drastically after upgrading the database from Oracle 102.0.4 to Oracle 11.2.0.3
- From: Hans Forbrich <fuzzy.graybeard@xxxxxxxxx>
- To: oracle-l@xxxxxxxxxxxxx
- Date: Sun, 11 Jan 2015 08:54:54 -0700
On 09/01/2015 5:21 PM, Ls Cheng wrote:
I always have a doubt, why people set SGA_TARGET smaller than
SGA_MAX_SIZE. What is the objective of doing so?
On systems that support Dynamic [reallocatoon of] Shared Memory, which
have several instances with varying work loads, the sum of SGA_TARGET
plus the sum of PGA_AGGREGATE_TARGET should be less than physical
memory, but the sum of SGA_MAX_SIZE plus the sum of PGA_AGGREGATE_TARGET
can exceed the physical memory, preallocating the fixed SGA portion for
each instance based on the maximums, permitting SGA_TARGETs to be
adjusted without restarts.
Very limited use case, but important for avoiding outages for such a
simple reconfiguration. Potentially significant for Multitenant
architecture.
/Hans
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