Re: Partitionining perfortmance degraded drastically after upgrading the database from Oracle 102.0.4 to Oracle

From: Hans Forbrich <>
Date: Sun, 11 Jan 2015 08:54:54 -0700
Message-ID: <>

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.


Received on Sun Jan 11 2015 - 16:54:54 CET

Original text of this message