Database Reference
In-Depth Information
Resources and locks are allocated in GRD and maintained by GES layer processes. These components are the key
pieces for the global locking scheme.
1
SGA Memory Allocation
GRD is stored in the shared_pool area of instance SGA. The memory allocations for GES resources and locks are
tagged as
ges resources
and
ges enqueues
. As the size of SGA and activity grows, these memory areas can grow
dynamically too. In the following output, 65MB is allocated for
ges resource
and 150MB for
ges enqueues
. The size
of GCS layer resources and locks is proportional to the size of SGA.
SELECT name, TRUNC(bytes/1024/1024, 2) size_MB
FROM v$sgastat
WHERE name LIKE 'ges resource%'
OR name LIKE 'ges enqueues'
OR name LIKE 'gcs resources'
OR name LIKE 'gcs enqueues'
OR name LIKE 'gcs shadows';
NAME SIZE_MB
-------------------------- ----------
ges resource 65.77
ges enqueues 150.37
gcs resources 599.44
gcs shadows 441.69
In version 12c, ges resource memory allocations are fine-grained into permanent and dynamic resource
allocations. The following shows the output of the earlier query.
NAME SIZE_MB
-------------------------- ----------
ges resource dynamic 10.81
ges resource permanent 45.87
...
You can gather statistics about dynamic growth or shrinkage by reviewing v$resource_limit view. In the
following output, resources grew up to a count of 689,253. However, current utilization is 123,090. This dynamic
growth or shrinkage is not necessarily a concern unless SGA memory allocations for resources and enqueues are
growing rapidly.
SELECT * FROM v$resource_limit WHERE resource_name IN
('ges_ress','ges_locks', 'gcs_resources','gcs_shadows');
1
In version 12c, the pluggable database feature is introduced. GES and GCS services are common services for both pluggable
databases and container databases, meaning both memory and background processes are shared between container and plugged
databases. So, structures discussed in this chapter have a new column, con_id, to support the pluggable database feature.
