Tuning Global Cache - Expert Oracle RAC Performance Diagnostics and Tuning - page 384

SGA

Streams Pool

Java Pool Fixed SGA

Shared Pool

Large Pool

gcs scan queue

CGS system incarn array

LMS post requested
array

PX msg pool

gcs res hash bucket

Check point Queue

gcs process descript gcs opaque in

Others

gcs mastership bucket

gcs res latch table

Database Buffer
Cache

gcs affinity gcs commit SGA st

gcs res latch table gcs pnp histo

other gcs buffers gcs enqueue mult

ges big msg buffer ges resource pools

ges shared global ges procs hash table ges_procs ges_ress

ges regular msg
buffers

ges deadlock xld
hash tab

ges_locks ges_cache_ress

ges reserved msg
buffers

ges deadlock xld
freelist

gcs resources

ges resources

Redo Log
Buffer

ges enqueues

gcs shadows

Global Resource Directory

Global Enqueue Service Global Cache Service

CKPT

LMDn LMON LMHB PING IPC0 LMSn DBWn

Private interconnect

Figure 13-2. Global cache

■ Figure 13-2 does not illustrate all of the global cache and global enqueue buffers; those that could not be
illustrated have been grouped under the other gcs buffers category.

Note

Resources available on any machine or to an Oracle instance are limited, meaning resources are not available
in abundance and that if a process on the system would need them, they may not be immediately available. There is
a physical limit on the amount of resources available on any system. For example, the processor resources is limited
by the number of CPUs available on the system; the amount of memory or cache area is limited by the amount of
physical memory available on the system and its availability depends on how busy the system is. Now for an Oracle
process, this is further limited by the actual amount of memory allocated to the SGA. Within the SGA, the shared pool,
the buffer cache, and so forth, are again preallocated from the total SGA (defined by the SGA_TARGET_SIZE parameter).
These are memory allocations used by a regular single-instance configuration.