Initialization Parameters, 54 of 188

GC_ROLLBACK_LOCKS

Parameter type:
String

Syntax:
GC_ROLLBACK_LOCKS =
'{rs_list=lock_count[!blocks][R][EACH])[:...])'
Spaces are not allowed within the quotation marks.

Parameter class:
Static

Default value:
0-128=32!8REACH

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_ROLLBACK_LOCKS is an Oracle Parallel Server parameter that specifies, for each rollback segment, the number of distributed locks available for simultaneously modified rollback segment blocks. The default is adequate for most applications.
These instance locks are acquired in exclusive mode by the instance that acquires the rollback segment. The locks force the instance to write rollback segment blocks to disk when another instance needs a read-consistent version of a block.
The syntax elements have the following meaning:

rs_list

is one or more rollback segments listed by their segment numbers, or ranges of segment numbers, with comma separators:
segnumber[-segnumber][,segnumber[-segnumber]]...

To find the correspondence between segment names and segment numbers, query SEGMENT_NAME and SEGMENT_ID columns of the data dictionary view "DBA_ROLLBACK_SEGS".
By default, any rollback segments that you do not specify in this parameter are covered by releasable locks. For information on releasable locks, see "GC_RELEASABLE_LOCKS".

lock_count

is the number of PCM locks assigned to rs_list. By default these locks are fixed. If you set lock_count to 0, then Oracle uses fine-grain locking for these segments and takes locks as needed from the pool of releasable locks

!blocks

specifies the number of contiguous blocks covered by one lock. The default is noncontiguous blocks.

R

indicates that these locks are releasable and are drawn as needed from the pool of releasable locks. If no blocks from rs_list are in the buffer cache, then no locks are taken from the releasable pool.

EACH

indicates that each rollback segment in rs_list is assigned a separate set of lock_count PCM locks.

A colon (:) separates each clause that assigns a number of PCM locks to rs_list.
See Also: Oracle8i Parallel Server Administration, Deployment, and Performance for more information on setting this parameter.

Parameter type:	String
Syntax:	GC_ROLLBACK_LOCKS = '{rs_list=lock_count[!blocks][R][EACH])[:...])' Spaces are not allowed within the quotation marks.
Parameter class:	Static
Default value:	`0-128=32!8REACH`
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_ROLLBACK_LOCKS` is an Oracle Parallel Server parameter that specifies, for each rollback segment, the number of distributed locks available for simultaneously modified rollback segment blocks. The default is adequate for most applications. These instance locks are acquired in exclusive mode by the instance that acquires the rollback segment. The locks force the instance to write rollback segment blocks to disk when another instance needs a read-consistent version of a block. The syntax elements have the following meaning:
`rs_list`	is one or more rollback segments listed by their segment numbers, or ranges of segment numbers, with comma separators: segnumber[-segnumber][,segnumber[-segnumber]]...
	To find the correspondence between segment names and segment numbers, query `SEGMENT_NAME` and `SEGMENT_ID` columns of the data dictionary view "DBA_ROLLBACK_SEGS". By default, any rollback segments that you do not specify in this parameter are covered by releasable locks. For information on releasable locks, see "GC_RELEASABLE_LOCKS".
`lock_count`	is the number of PCM locks assigned to rs_list. By default these locks are fixed. If you set lock_count to 0, then Oracle uses fine-grain locking for these segments and takes locks as needed from the pool of releasable locks
`!blocks`	specifies the number of contiguous blocks covered by one lock. The default is noncontiguous blocks.
`R`	indicates that these locks are releasable and are drawn as needed from the pool of releasable locks. If no blocks from rs_list are in the buffer cache, then no locks are taken from the releasable pool.
`EACH`	indicates that each rollback segment in rs_list is assigned a separate set of lock_count PCM locks.
A colon (:) separates each clause that assigns a number of PCM locks to rs_list. See Also: Oracle8i Parallel Server Administration, Deployment, and Performance for more information on setting this parameter.