Name

ALTER SNAPSHOT

Synopsis

ALTER SNAPSHOT
[schema.]snapshot_name
   [PCTFREE integer]
   [PCTUSED integer]
   [INITRANS integer]
   [MAXTRANS integer]
   [LOGGING | NOLOGGING]
   [CACHE | NOCACHE]
   [STORAGE (
      [NEXT integer[K | M] ]
      [MAXEXTENTS {integer | UNLIMITED} ]
      [PCTINCREASE integer]
      [FREELISTS integer]
      [FREELIST GROUPS integer] ]
      ) ]
[PARALLEL ( {DEGREE {integer | DEFAULT} |
INSTANCES {integer | DEFAULT} } ) ]
   [NOPARALLEL]
   [USING INDEX
      [PCTFREE integer]
      [INITRANS integer]
      [MAXTRANS integer]
      [LOGGING | NOLOGGING]
      [STORAGE (
         [INITIAL integer[K | M] ]
         [NEXT integer[K | M] ]
         [MINEXTENTS integer]
[MAXEXTENTS {integer | UNLIMITED} ]
         [PCTINCREASE integer]
         [FREELISTS integer]
         [FREELIST GROUPS integer]
           ) ]
   ]
   [REFRESH
      [FAST | COMPLETE | FORCE]
      [START WITH date]
      [NEXT date]
      [WITH PRIMARY KEY]
      [USING DEFAULT [MASTER | LOCAL ] ROLLBACK SEGMENT] |
[USING [MASTER | LOCAL] ROLLBACK SEGMENT
rollback_segment]
   ]

Changes the storage characteristics or automatic refresh characteristics of a snapshot (snapshot_name).

Keywords

PCTFREE

Specifies the percentage of space to be reserved in each data block for future updates to rows contained in that block. Valid values are - 99, and the default value is 10.

PCTUSED

Specifies the minimum percentage of space that will be maintained as used in each data block. Valid values are 1- 99, and the default value is 40.

INITRANS

Specifies the initial number of transaction entries allocated to each block.

MAXTRANS

Specifies the maximum number of transaction entries allocated to each block.

LOGGING

Specifies that the operation is to be logged to the redo logs.

NOLOGGING

Specifies that nothing is to be written to the redo logs for this operation.

CACHE

Specifies how many sequence numbers Oracle will pregenerate and keep in memory. Note that when the database is shut down, unused sequence numbers stored in cache will be lost. The default is 20.

NOCACHE

Specifies that no sequence numbers are pregenerated to memory.

STORAGE

Specifies the physical characteristics of the snapshot 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 snapshot. 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 snapshot. The default is 1, and the maximum depends on the database blocksize.

FREELIST GROUPS

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

PARALLEL

Specifies the level of parallelism to be supported, based on the following parameters:

DEGREE

Specifies the degree of parallelism. An integer value specifies how many slave processes can be used. Specify DEFAULT to use the default value for the tablespace.

INSTANCES

Specifies the number of instances that can be used to execute slave processes. Specify DEFAULT to use the default value specified for the tablespace.

NOPARALLEL

Specifies that no parallel processing will be supported for the snapshot.

USING INDEX

Changes the value of the PCTFREE, INITRANS, MAXTRANS, and STORAGE parameters for the index Oracle uses to maintain the snapshot’s data. If the index is being created, you can also specify:

INITIAL

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

MINEXTENTS

Specifies the number of extents to be allocated when this snapshot is created. The minimum and default value is 1.

REFRESH

Specifies the mode and times for automatic refreshes. FAST means use the snapshot log associated with the master table. COMPLETE means refresh by reexecuting the snapshot’s query. FORCE is the default, and means that Oracle will either decide that a FAST refresh is possible or do a COMPLETE refresh.

START WITH

Specifies a date for the next automatic refresh time, using a standard Oracle date expression.

NEXT

Specifies a new date expression for calculating the interval between automatic refreshes.

USING DEFAULT ROLLBACK SEGMENT

Specifies the rollback segment to be used as a default if a rollback segment is not explicitly supplied. Select either MASTER (use the default rollback segment at the remote master for the individual snapshot) or LOCAL (use the default rollback segment for the local refresh group that contains the snapshot).

USING ROLLBACK SEGMENT rollback_segment

Specifies the rollback segment to use when refreshing the snapshot. Specify either MASTER (the rollback segment to be used at the remote master for the individual snapshot) or LOCAL (specifies the rollback segment to be used for the local refresh group that contains the snapshot).

Note

You must own the snapshot or have the ALTER ANY SNAPSHOT privilege to issue this command.

Example

The following example causes scott’s snapshot dept_snap to be refreshed at midnight tomorrow, and then every week:

ALTER SNAPSHOT scott.dept_snap
   REFRESH COMPLETE
   START WITH SYSDATE+1
   NEXT SYSDATE+7
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