V$PGASTAT

Thank you for visiting Spatial DBA - Oracle and ArcSDE.

I have stopped updating the blog.

Please visit Oracle DBA Tips (http://www.oracledbatips.com) for more Oracle DBA Tips.
==================================================================
 



Oracle 11gR1
V$PGASTAT displays PGA memory usage statistics as well as statistics about the automatic PGA memory manager when it is enabled (that is, when PGA_AGGREGATE_TARGET is set). Cumulative values in V$PGASTAT are accumulated since instance startup.

Column	Datatype	Description
NAME	VARCHAR2(64)	Name of the statistic (see table below)
VALUE	NUMBER	Statistic value
UNIT	VARCHAR2(12)	Unit for the value: · bytes · microseconds · percent

V$PGASTAT Statistics

Statistic Name	Description
aggregate PGA target parameter	Current value of the PGA_AGGREGATE_TARGET initialization parameter. If this parameter is not set, then its value is 0 and automatic management of PGA memory is disabled.
aggregate PGA auto target	Amount of PGA memory the Oracle Database can use for work areas running in automatic mode. This amount is dynamically derived from the value of the PGA_AGGREGATE_TARGET initialization parameter and the current work area workload, and continuously adjusted by the Oracle Database. If this value is small compared to the value of PGA_AGGREGATE_TARGET, then a large amount of PGA memory is used by other components of the system (for example, PL/SQL or Java memory) and little is left for work areas. The DBA must ensure that enough PGA memory is left for work areas running in automatic mode.
global memory bound	Maximum size of a work area executed in automatic mode. This value is continuously adjusted by the Oracle Database to reflect the current state of the work area workload. The global memory bound generally decreases when the number of active work areas is increasing in the system. If the value of the global bound decreases below 1 MB, then the value of PGA_AGGREGATE_TARGET should be increased.
total PGA allocated	Current amount of PGA memory allocated by the instance. The Oracle Database attempts to keep this number below the value of the PGA_AGGREGATE_TARGET initialization parameter. However, it is possible for the PGA allocated to exceed that value by a small percentage and for a short period of time when the work area workload is increasing very rapidly or when PGA_AGGREGATE_TARGET is set to a small value.
total PGA used	Indicates how much PGA memory is currently consumed by work areas. This number can be used to determine how much memory is consumed by other consumers of the PGA memory (for example, PL/SQL or Java).
total PGA used for auto workareas	Indicates how much PGA memory is currently consumed by work areas running under the automatic memory management mode. This number can be used to determine how much memory is consumed by other consumers of the PGA memory (for example, PL/SQL or Java).
total PGA used for manual workareas	Indicates how much PGA memory is currently consumed by work areas running under the manual memory management mode. This number can be used to determine how much memory is consumed by other consumers of the PGA memory (for example, PL/SQL or Java).
over allocation count	This statistic is cumulative since instance startup. Over allocating PGA memory can happen if the value of PGA_AGGREGATE_TARGET is too small. When this happens, the Oracle Database cannot honor the value of PGA_AGGREGATE_TARGET and extra PGA memory needs to be allocated. If over allocation occurs, then increase the value of PGA_AGGREGATE_TARGET using the information provided by the V$PGA_TARGET_ADVICE view.
bytes processed	Number of bytes processed by memory intensive SQL operators, cumulated since instance startup.
extra bytes read/written	Number of bytes processed during extra passes of the input data, cumulated since instance startup. When a work area cannot run optimal, one or more of these extra passes is performed.
cache hit percentage	A metric computed by the Oracle Database to reflect the performance of the PGA memory component, cumulative since instance startup. A value of 100% means that all work areas executed by the system since instance startup have used an optimal amount of PGA memory. When a work area cannot run optimal, one or more extra passes is performed over the input data. This will reduce the cache hit percentage in proportion to the size of the input data and the number of extra passes performed.

Note:

1. SELECT * FROM V$PGASTAT;

NAME	VALUE	UNIT
aggregate PGA target parameter	104857600	bytes
aggregate PGA auto target	67977216	bytes
global memory bound	20971520	bytes
total PGA inuse	29320192	bytes
total PGA allocated	55439360	bytes
maximum PGA allocated	128949248	bytes
total freeable PGA memory	8650752	bytes
process count	21	NULL
max processes count	27	NULL
PGA memory freed back to OS	6334709760	bytes
total PGA used for auto workareas	0	bytes
maximum PGA used for auto workareas	21029888	bytes
total PGA used for manual workareas	0	bytes
maximum PGA used for manual workareas	537600	bytes
over allocation count	0	NULL
bytes processed	19439247360	bytes
extra bytes read/written	3792268288	bytes
cache hit percentage	83.67	percent
recompute count (total)	998308	NULL

Oracle dynamic performance views