OCP-042 LOGGING of the create tablespace ..

6. Which two statements regarding the LOGGING clause of the CREATE TABLESPACE. .. statement are
correct? (Choose two.)
A. This clause is not valid for a temporary or undo tablespace.
B. If the tablespace is in the NOLOGGING mode, no operation on the tablespace will generate redo.
C. The tablespace will be in the NOLOGGING mode by default, if not specified while creating a
tablespace.
D. The tablespacelevel
logging attribute can be overridden by logging specifications at the table, index,
materialized view, materialized view log, and partition levels.
Answer: AD

Logging_clause

Specify the default logging attributes of all tables, indexes, materialized views, materialized view logs, and partitions within the tablespace.  LOGGING  is the default. This clause is not valid for a temporary or undo tablespace.

The tablespace-level logging attribute can be overridden by logging specifications at the table, index, materialized view, materialized view log, and partition levels.

Purpose

The logging_clause lets you specify whether creation of a database object will be logged in the redo log file (LOGGING) or not (NOLOGGING).

You can specify the logging_clause in the following statements:

• CREATE TABLE and ALTER TABLE: for logging of the table, a table partition, a LOB segment, or the overflow segment of an index-organized table (seeCREATE TABLE and ALTER TABLE).

• CREATE INDEX and ALTER INDEX: for logging of the index or an index partition (see CREATE INDEX and ALTER INDEX).

• CREATE MATERIALIZED VIEW and ALTER MATERIALIZED VIEW: for logging of the materialized view, one of its partitions, or a LOB segment (see CREATE MATERIALIZED VIEW and ALTER MATERIALIZED VIEW).

• CREATE MATERIALIZED VIEW LOG and ALTER MATERIALIZED VIEW LOG: for logging of the materialized view log or one of its partitions (see CREATE MATERIALIZED VIEW LOG and ALTER MATERIALIZED VIEW LOG).

• CREATE TABLESPACE and ALTER TABLESPACE: to set or modify the default logging characteristics for all objects created in the tablespace (see CREATE TABLESPACE and ALTER TABLESPACE).

You can also specify LOGGING or NOLOGGING for the following operations:

• Rebuilding an index (using CREATE INDEX ... REBUILD)

• Moving a table (using ALTER TABLE ... MOVE)

Syntax

logging_clause::=

Description of the illustration logging_clause.gif

Semantics

This section describes the semantics of the logging_clause. For additional information, refer to the SQL statement in which you set or reset logging characteristics for a particular database object.

Specify LOGGING if you want the creation of a database object, as well as subsequent inserts into the object, to be logged in the redo log file.

Specify NOLOGGING if you do not want these operations to be logged.

• For a nonpartitioned object, the value specified for this clause is the actual physical attribute of the segment associated with the object.

• For partitioned objects, the value specified for this clause is the default physical attribute of the segments associated with all partitions specified in the CREATE statement (and in subsequent ALTER ... ADD PARTITION statements), unless you specify the logging attribute in the PARTITION description.

If the object for which you are specifying the logging attributes resides in a database or tablespace in force logging mode, then Oracle Database ignores anyNOLOGGING setting until the database or tablespace is taken out of force logging mode.

If the database is run in archivelog mode, then media recovery from a backup made before the LOGGING operation re-creates the object. However, media recovery from a backup made before the NOLOGGING operation does not re-create the object.

The size of a redo log generated for an operation in NOLOGGING mode is significantly smaller than the log generated in LOGGING mode.

In NOLOGGING mode, data is modified with minimal logging (to mark new extents INVALID and to record dictionary changes). When applied during media recovery, the extent invalidation records mark a range of blocks as logically corrupt, because the redo data is not fully logged. Therefore, if you cannot afford to lose the database object, then you should take a backup after the NOLOGGING operation.

NOLOGGING is supported in only a subset of the locations that support LOGGING. Only the following operations support the NOLOGGING mode:

DML:  

• Direct-path INSERT (serial or parallel) resulting either from an INSERT or a MERGE statement. NOLOGGING is not applicable to any UPDATE operations resulting from the MERGE statement.

• Direct Loader (SQL*Loader)

DDL:  

• CREATE TABLE ... AS SELECT

• CREATE TABLE ... LOB_storage_clause ... LOB_parameters ... NOCACHE | CACHE READS

• ALTER TABLE ... LOB_storage_clause ... LOB_parameters ... NOCACHE | CACHE READS (to specify logging of newly created LOB columns)

• ALTER TABLE ... modify_LOB_storage_clause ... modify_LOB_parameters ... NOCACHE | CACHE READS (to change logging of existing LOB columns)

• ALTER TABLE ... MOVE

• ALTER TABLE ... (all partition operations that involve data movement)

  • ALTER TABLE ... ADD PARTITION (hash partition only)

  • ALTER TABLE ... MERGE PARTITIONS

  • ALTER TABLE ... SPLIT PARTITION

  • ALTER TABLE ... MOVE PARTITION

  • ALTER TABLE ... MODIFY PARTITION ... ADD SUBPARTITION

  • ALTER TABLE ... MODIFY PARTITION ... COALESCE SUBPARTITION

• CREATE INDEX

• ALTER INDEX ... REBUILD

• ALTER INDEX ... REBUILD [SUB]PARTITION

• ALTER INDEX ... SPLIT PARTITION

For objects other than LOBs, if you omit this clause, then the logging attribute of the object defaults to the logging attribute of the tablespace in which it resides.

For LOBs, if you omit this clause:

• If you specify CACHE, then LOGGING is used (because you cannot have CACHE NOLOGGING).

• If you specify NOCACHE or CACHE READS, then the logging attribute defaults to the logging attribute of the tablespace in which it resides.

NOLOGGING does not apply to LOBs that are stored inline with row data. That is, if you specify NOLOGGING for LOBs with values less than 4000 bytes and you have not disabled STORAGE IN ROW, then Oracle ignores the NOLOGGING specification and treats the LOB data the same as other table data.

FORCE LOGGING

Use this clause to put the tablespace into FORCE LOGGING mode. Oracle Database will log all changes to all objects in the tablespace except changes to temporary segments, overriding any NOLOGGING setting for individual objects. The database must be open and in READ WRITE mode.

This setting does not exclude the NOLOGGING attribute. That is, you can specify both FORCE LOGGING and NOLOGGING. In this case, NOLOGGING is the default logging mode for objects subsequently created in the tablespace, but the database ignores this default as long as the tablespace or the database is in FORCE LOGGINGmode. If you subsequently take the tablespace out of FORCE LOGGING mode, then the NOLOGGING default is once again enforced.

Note:

FORCE  LOGGING mode can have performance effects. Please refer to  Oracle Database Administrator's Guide for information on when to use this setting.

Restriction on Forced Logging You cannot specify FORCE LOGGING for an undo or temporary tablespace.