DBA_HIST_PGA_TARGET_ADVICE

DBA_HIST_PGA_TARGET_ADVICE displays historical predictions of how the cache hit percentage and over allocation count statistics displayed by the V$PGASTAT performance view would be impacted if the value of the PGA_AGGREGATE_TARGET parameter is changed. This view contains snapshots of V$PGA_TARGET_ADVICE.

Column	Datatype	NULL	Description
`SNAP_ID`	`NUMBER`	`NOT NULL`	Unique snapshot ID
`DBID`	`NUMBER`	`NOT NULL`	Database ID for the snapshot
`INSTANCE_NUMBER`	`NUMBER`	`NOT NULL`	Instance number for the snapshot
`PGA_TARGET_FOR_ESTIMATE`	`NUMBER`	`NOT NULL`	Value of `PGA_AGGREGATE_TARGET` for the prediction (in bytes)
`PGA_TARGET_FACTOR`	`NUMBER`		`PGA_TARGET_FOR_ESTIMATE` / the current value of the `PGA_AGGREGATE_TARGET` parameter
`ADVICE_STATUS`	`VARCHAR2(3)`		Indicates whether the advice is enabled (`ON`) or disabled (`OFF`) depending on the value of the `STATISTICS_LEVEL` parameter
`BYTES_PROCESSED`	`NUMBER`		Total bytes processed by all the work areas considered by this advice (in bytes)
`ESTD_TIME`	`NUMBER`		Time (in seconds) required to process the bytes
`ESTD_EXTRA_BYTES_RW`	`NUMBER`		Estimated number of extra bytes which would be read or written if `PGA_AGGREGATE_TARGET` was set to the value of the `PGA_TARGET_FOR_ESTIMATE` column. This number is derived from the estimated number and size of work areas which would run in one-pass (or multi-pass) for that value of `PGA_AGGREGATE_TARGET`.
`ESTD_PGA_CACHE_HIT_PERCENTAGE`	`NUMBER`		Estimated value of the cache hit percentage statistic when `PGA_AGGREGATE_TARGET` equals `PGA_TARGET_FOR_ESTIMATE`. This column is derived from the above two columns and is equal to `BYTES_PROCESSED` / (`BYTES_PROCESSED` + `ESTD_EXTRA_BYTES_RW`)
`ESTD_OVERALLOC_COUNT`	`NUMBER`		Estimated number of PGA memory over-allocations if the value of `PGA_AGGREGATE_TARGET` is set to `PGA_TARGET_FOR_ESTIMATE`. A nonzero value means that `PGA_TARGET_FOR_ESTIMATE` is not large enough to run the work area workload. Hence, `PGA_AGGREGATE_TARGET` should not be set to `PGA_TARGET_FOR_ESTIMATE` since Oracle will not be able to honor that target.
`CON_DBID`	`NUMBER`		The database ID of the PDB for the sampled session
`CON_ID`	`NUMBER`		The ID of the container that `CON_DBID` identifies. Possible values include: `0`: This value is used for rows containing data that pertain to the entire CDB. This value is also used for rows in non-CDBs. `1`: This value is used for rows containing data that pertain to only the root n: Where n is the applicable container ID for the rows containing data