Name

ALTER ROLLBACK SEGMENT

Synopsis

ALTER ROLLBACK SEGMENT segment_name
   [ONLINE | OFFLINE]
   [STORAGE (
      [NEXT integer[K | M] ]
      [MAXEXTENTS {integer | UNLIMITED} ]
      [PCTINCREASE integer]
      [FREELISTS integer]
      [FREELIST GROUPS integer]
      [OPTIMAL {integer[K | M] | NULL} ]
      ) ]
   [SHRINK TO integer[K | M] ]

Changes the online status of a rollback segment (segment_name) or modifies its storage characteristics.

Keywords

ONLINE

Specifies that the named rollback segment is to be brought online.

OFFLINE

Specifies that the named rollback segment is to be taken offline.

STORAGE

Specifies the physical characteristics of the rollback segment as follows:

NEXT

Specifies the size of the next extent in bytes, kilobytes, or megabytes. If the value is not a multiple of the database blocksize, it will be rounded up to a multiple of the database blocksize.

MAXEXTENTS

Specifies the maximum number of extents that may be allocated for this rollback segment. The default will vary according to the database blocksize. Specify UNLIMITED for unlimited expansion.

PCTINCREASE

Specifies the percentage by which each extent will grow over the previous extent. The default is 50, which means that each extent will be one-and-one-half times larger than the previous extent.

FREELISTS

Specifies the number of free lists contained in each freelist group in this rollback segment. The default is 1, and the maximum depends on the database blocksize.

FREELIST GROUPS

Specifies the number of groups of free lists for this rollback segment. The default is 1. This parameter should be used only with the Parallel Server option running in parallel mode.

OPTIMAL

Specifies the optimal size for this rollback segment. Oracle will attempt to maintain this size by deallocating unused extents. The default is NULL, which means no deallocation will ever take place.

SHRINK TO

Specifies that the named rollback segment should be reduced in size TO the size specified (in kilobytes or megabytes), or to the OPTIMAL size if no size is specified.

Note

You must have the ALTER ROLLBACK SEGMENT privilege to issue this command.

Examples

The following example takes rollback segment RBS02 offline:

ALTER ROLLBACK SEGMENT RBS02 OFFLINE

The following example changes the storage allocation for RBS02 so that each extent will be 30K, its optimal size will be 60K, and a maximum of 10 extents will be permitted:

ALTER ROLLBACK SEGMENT RBS02 
          STORAGE (NEXT 30K MAXEXTENTS 10 OPTIMAL 60K)
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