Oracle8i Reference
Release 2 (8.1.6)

Part Number A76961-01





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Initialization Parameters, 52 of 188


Parameter type: 





Spaces are not allowed within the quotation marks. 

Parameter class: 


Default value: 


Oracle Parallel Server: 

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. 

GC_FILES_TO_LOCKS is an Oracle Parallel Server parameter that has no effect on an instance running in exclusive mode. It controls the mapping of parallel cache management (PCM) locks to datafiles.

The syntax elements have the following meaning: 


is 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 FILE_NAME and FILE_ID columns of the data dictionary view "DBA_DATA_FILES".

By default, any datafiles that you do not specify in this parameter are covered by releasable locks. For information on releasable locks, see "GC_RELEASABLE_LOCKS"


is the number of PCM locks assigned to file_list. By default these locks are fixed. If you set lock_count to 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 these locks are releasable and are drawn as needed from the pool of releasable locks. If no blocks from file_list are in the buffer cache, then no locks are taken from the releasable pool. 


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 Parallel Server.

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 file_list.

See Also: Oracle8i Parallel Server Administration, Deployment, and Performance for more information on setting this parameter. 

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