Saturday, October 29, 2011

Very good summary of DELETE TRUNCATE and DROP commands

Hello everyone,

Today i came across a very good explanation of  DELETE TRUNCATE and DROP commands.


Tuesday, October 11, 2011


Oracle gives us the ability to limit redo generation on tables and indexes by setting them in NOLOGGING mode.

NOLOGGING affect the recoverability. Before going into how to limit the redo generation, it is important to clear the misunderstanding that NOLOGGING is the way out of redo generation, there are some points regarding it:

NOLOGGING is designed to handle bulk inserts of data which can be easy reproduced.

Regardless of LOGGING status, writing to undo blocks causes generation of redo.
LOGGING should not be disabled on a primary database if it has one or more standby databases. For this reason oracle introduced the ALTER DATABASE FORCE LOGGING command in Oracle 9i R2. (Means that the NOLOGGING attribute will not have any effect on the segments) If the database is in FORCE LOGGING MODE. NOLOGGING can be also override at tablespace level using ALTER TABLESPACE … FORCE LOGGING.

FORCE LOGGING can be used on tablespace or database level to force logging of changes to the redo. This may be required for sites that are mining log data, using Oracle Streams or using Data Guard (standby databases).