ALTER MATERIALIZED ZONEMAP

Purpose

Use the ALTER MATERIALIZED ZONEMAP statement to modify an existing zone map in one of the following ways:

• To change its attributes

• To change its default refresh method and mode

• To enable or disable its use for pruning

• To compile it, rebuild it, or make it unusable

Prerequisites

The zone map must be in your own schema or you must have the ALTER ANY MATERIALIZED VIEW system privilege.

The user who owns the schema containing the zone map must have access to any base tables of the zone map that reside outside of that schema, either through a READ or SELECT object privilege on each of the tables, or through the READ ANY TABLE or SELECT ANY TABLE system privilege.

Syntax

alter_materialized_zonemap::=

alter_zonemap_attributes::=

zonemap_refresh_clause::=

Semantics

schema

Specify the schema containing the zone map. If you omit schema, then Oracle Database assumes the zone map is in your own schema.

zonemap_name

Specify the name of the zone map to be altered.

alter_zonemap_attributes

Use this clause to modify the following attributes for the zone map: PCTFREE, PCTUSED, and CACHE or NOCACHE. These attributes have the same semantics for ALTER MATERIALIZED ZONEMAP and CREATE MATERIALIZED ZONEMAP. For complete information on these attributes, refer to PCTFREE, PCTUSED, and CACHE | NOCACHE in the documentation on CREATE MATERIALIZED ZONEMAP.

zonemap_refresh_clause

Use this clause to modify the default refresh method and mode for the zone map. This clause has the same semantics for ALTER MATERIALIZED ZONEMAP and CREATE MATERIALIZED ZONEMAP. For complete information on this clause, refer to zonemap_refresh_clause in the documentation on CREATE MATERIALIZED ZONEMAP.

ENABLE | DISABLE PRUNING

Use this clause to enable or disable use of the zone map for pruning. This clause has the same semantics for ALTER MATERIALIZED ZONEMAP and CREATE MATERIALIZED ZONEMAP. For complete information on this clause, refer to ENABLE | DISABLE PRUNING in the documentation on CREATE MATERIALIZED ZONEMAP

COMPILE

This clause lets you explicitly compile the zone map. This operation validates the zone map after a DDL operation changes the structure of one or more of its base tables. It is usually not necessary to issue this clause because Oracle database automatically compiles a zone map that requires compilation before using it. However, if you would like to explicitly compile a zone map, then you can use this clause to do so.

The result of compiling a zone map depends on whether a base table is changed in a way that affects the zone map. For example, if a column is added to a base table, then the zone map will be valid after compilation because the change does not affect the zone map. However, if a column that is included in the defining subquery of the zone map is dropped from a base table, then the zone map will be invalid after compilation.

You can determine if a zone map requires compilation by querying the COMPILE_STATE column of the ALL_, DBA_, and USER_ZONEMAPS data dictionary views. If the value of the column is NEEDS_COMPILE, then the zone map requires compilation.

REBUILD

This clause lets you explicitly rebuild the zone map. This operation refreshes the data in the zone map. This clause is useful in the following situations:

• You can use this clause to refresh the data for a refresh-on-demand zone map. Refer to the ON DEMAND clause in the documentation on CREATE MATERIALIZED ZONEMAP for more information.

• You must issue this clause after an EXCHANGE PARTITION operation on one of the base tables of a zone map, regardless of the default refresh mode of the zone map.

• If a zone map is marked unusable, then you must issue this clause to mark it usable. You can determine if a zone map is marked unusable by querying the UNUSABLE column of the ALL_, DBA_, and USER_ZONEMAPS data dictionary views.

UNUSABLE

Specify this clause to make the zone map unusable. Subsequent queries will not use the zone map and the database will no longer maintain the zone map. You can make the zone map usable again by issuing an ALTER MATERIALIZED ZONEMAP ... REBUILD statement.

Examples

Modifying Zone Map Attributes: Example The following statement modifies the PCTFREE and PCTUSED attributes of zone map sales_zmap, and modifies the zone map so that it does not use caching:

ALTER MATERIALIZED ZONEMAP sales_zmap
  PCTFREE 20 PCTUSED 50 NOCACHE;

Modifying the Default Refresh Method and Mode for a Zone Map: Example The following statement changes the default refresh method to FAST and the default refresh mode to ON COMMIT for zone map sales_zmap:

ALTER MATERIALIZED ZONEMAP sales_zmap
  REFRESH FAST ON COMMIT;

Disabling Use of a Zone Map for Pruning: Example The following statement disables use of zone map sales_zmap for pruning:

ALTER MATERIALIZED ZONEMAP sales_zmap
  DISABLE PRUNING;

Compiling a Zone Map: Example The following statement compiles zone map sales_zmap:

ALTER MATERIALIZED ZONEMAP sales_zmap
  COMPILE;

Rebuilding a Zone Map: Example The following statement rebuilds zone map sales_zmap:

ALTER MATERIALIZED ZONEMAP sales_zmap
  REBUILD;

Making a Zone Map Unusable: Example The following statement makes zone map sales_zmap unusable:

ALTER MATERIALIZED ZONEMAP sales_zmap
  UNUSABLE;