|Oracle® Database Reference
10g Release 2 (10.2)
|PDF · Mobi · ePub|
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|Default value||There is no default value.|
|Real Application Clusters||You must set this parameter for every instance, and multiple instances must have identical values. To change the value, you must shut down all instances in the cluster, change the value for each instance, and then start up each instance.|
Note:Setting this parameter to any value other than the default will disable Cache Fusion processing in a Real Application Clusters environment.
GC_FILES_TO_LOCKS is a Real Application Clusters parameter that has no effect on an instance running in exclusive mode. It controls the mapping of pre-release 9.0.1 parallel cache management (PCM) locks to datafiles.
One or more datafiles listed by their file numbers, or ranges of file numbers, with comma separators:
To find the correspondence between filenames and file numbers, query the
FILE_ID columns of the
DBA_DATA_FILES data dictionary view.
The number of PCM locks assigned to
file_list. By default these locks are fixed. If you set
0, then Oracle uses fine-grain locking for these files and takes locks as needed from the pool of releasable locks.
Specifies the number of contiguous blocks covered by one lock. The default is noncontiguous blocks.
Indicates that each datafile in
file_list is assigned a separate set of
lock_count PCM locks.
The value of the parameter should be set to cover as many files as possible. Therefore, to avoid performance problems, you should always change
GC_FILES_TO_LOCKS when the size of datafiles change or when new datafiles are added. Doing so requires you to shut down and restart your cluster database.
If the number of PCM locks allocated to a datafile is less than or equal to the number of blocks in a datafile, each of these locks will cover a number of contiguous blocks within the datafile equal to
blocks. If the number of PCM locks assigned to the datafile is larger than its number of blocks, resources will be wasted because some locks will not be covering any blocks.
A colon (:) separates each clause that assigns a number of PCM locks to
See Also:Oracle Database Oracle Clusterware and Oracle Real Application Clusters Administration and Deployment Guide and the Oracle Database Oracle Clusterware and Oracle Real Application Clusters Installation Guide for your operating system for more information on setting this parameter