Saturday, April 9, 2011

Memory management SGA PGA

RAM=16 GB
WINDOW PROCESS=16*20%=3.2 GB

ORACLE SERVICES=12 GB

PGA_AGGREGATE_TARGET==(RAM*80%)*50% FOR DSS
PGA_AGGREGATE_TARGET==(RAM*80%)*20% FOR OLTP


SGA_TARGET + PGA_AGGREGATE_TARGET determine how much memory oracle is going to use.

SGA_MAX_SIZE is only upper limit. Not how much oracle is going to allocate.


PGA_AGGREGATE_TARGET is not being allocated at the startup it is allocated on as needed basis, so when some server process need memory from pga_aggregate _target area this memory is being allocated by setting 1GB to PGA_AGGREGATE_TARGET you set max size for this region, so even if some process will need memory but you have already reached 1GB Oracle will not allocate more.

INSTANCE =3



SGA PGA TOTAL
YR 0910 1 0.5 1.5
YR 1011 1 0.5 1.5
YR 1112 6 3 9











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