|Oracle® Database Administrator's Guide
11g Release 2 (11.2)
Part Number E17120-11
|PDF · Mobi · ePub|
For some database operations, you can control whether the database generates redo records. Without redo, no media recovery is possible. However, suppressing redo generation can improve performance, and may be appropriate for easily recoverable operations. An example of such an operation is a
CREATE TABLE...AS SELECT statement, which can be repeated in case of database or instance failure.
NOLOGGING clause in the
CREATE TABLESPACE statement to suppress redo when these operations are performed for objects within the tablespace. If you do not include this clause, or if you specify
LOGGING instead, then the database generates redo when changes are made to objects in the tablespace. Redo is never generated for temporary segments or in temporary tablespaces, regardless of the logging attribute.
The logging attribute specified at the tablespace level is the default attribute for objects created within the tablespace. You can override this default logging attribute by specifying
NOLOGGING at the schema object level--for example, in a
CREATE TABLE statement.
If you have a standby database,
NOLOGGING mode causes problems with the availability and accuracy of the standby database. To overcome this problem, you can specify
FORCE LOGGING mode. When you include the
FORCE LOGGING clause in the
CREATE TABLESPACE statement, you force the generation of redo records for all operations that make changes to objects in a tablespace. This overrides any specification made at the object level.
If you transport a tablespace that is in
FORCE LOGGING mode to another database, the new tablespace will not maintain the
FORCE LOGGING mode.