Tuning Global Cache - Expert Oracle RAC Performance Diagnostics and Tuning - page 426

Data Dictionary Views to Monitor Global Cache
Oracle dynamic performance views provide a great insight into the performance statistics. These views provide great
instrumentation into the functioning and behavior of global cache in a RAC environment.

GV$INSTANCE_CACHE_TRANSFER
This view displays statistics for blocks transferred among instances in the cluster, the view captures data based on
where the data is originated; for example, in the outputs following, data is sent from instance 1 to other instances in
the cluster. The current block ( CUR_BLOCK ) is the most up-to-date copy containing all recent modifications, and the
consistent read block ( CR_BLOCK ) contains consistent read copy of the block prior to modifications. Cache transfer
statistics are collected for the classes listed in Table 13-2 for both CR blocks and CUR blocks.

Table 13-2. Cache Transfer Classes

Class Description

Data block Data blocks

Unused
Undo header Undo header information

Save undo header Undo header information

Bitmap index block Bitmap index block information

File header block File header block information

Free list Free list information if ASSM is not used for segment management

Undo block Undo block information

Segment header Segment header of data segment

Extent map Extent maps of the data files

Sort block Sort blocks

Save undo block Undo blocks saved

Bitmap block Bitmap blocks when local managed tablespace is used

Script: MVRACPDnTap_instCacheTrans.sql
SELECT INST_ID INT ,
INSTANCE TRG_INST,
CLASS ,
CR_BLOCK ,
CR_BLOCK_TIME/1000 CR_BLK_TIM,
CR_2HOP ,
CR_3HOP ,