Tuning Global Cache - Expert Oracle RAC Performance Diagnostics and Tuning - page 385

In a RAC environment, there are no parameters to allocate any global-specific resources such as global cache
size or global shared pool area. Oracle allocates a certain portion of the available resources from the shared pool
or SGA for global activity. The availability of global resources can be monitored using the view GV$RESOURCE_LIMIT .
For example, the workshop in the next section illustrates a small example on how the global cache section can
be monitored.
RAC memory resource usage of the shared pool can be monitored by querying the V$SGASTAT view for GCS, GES,
and KCL (kernel cache layer) related entries. Similarly, the current and maximum number of GCS resources/shadows
(resource names gcs_resources and gcs_shadows ) and GES resources/enqueues (resource names ges_ress and
ges_locks ) can be obtained by querying the V$RESOURCE_LIMIT views. In case there is a shortage of memory for the
GCS/GES related components, Oracle will dynamically allocate memory from the free memory pool in the shared
pool. It is recommended to carefully calculate the resources and enqueues as needed because dynamic memory
allocation from the shared pool is an expensive operation.
SQL> oradebug setmypid
SQL> oradebug call kjcsdmp
Workshop
In this workshop, we try to understand the sizing of the resources and state objects used by the GCS and GES in the SGA.
Step 1
The following query generates the output showing the current utilization of global resources:
Script: MVRACPDnTap_reslimit.sql
SELECT inst_id INT,
resource_name,
current_utilization CU,
max_utilization MU,
initial_allocation IA,
limit_value LV
FROM gv$resource_limit
WHERE max_utilization > 0
AND resource_name LIKE 'g%'
ORDER BY inst_id,
resource_name