Friday, April 9, 2010

Drop or Recreate DB Control In A 10g R2/11g Data

In Order to drop or reinstall Database Control (repository), you'll need to execute the following steps:

- /bin/emca -deconfig dbcontrol db -repos drop

This single command will delete both configuration files and repository objects.

- Create DB Control Objects
to create the DB Control Repository Objects and Configuration Files excute the following command:
bin/emca -config dbcontrol db -repos create

Thursday, April 8, 2010

Reducing disk I/O on Oracle database

How do we reduce disk I/O in UNIX? There are three generally accepted techniques for the DBA to reduce disk I/O:
1-Tune SQL statements to retrieve data with a minimum of disk I/O - This is generally performed by finding large-table full-table scans and replacing the full-table scan with an index scan.

2- Change the Oracle SGA - When we increase the shared_pool_size, large_pool_size, or db_cache_size, the resulting performance improvement is related to the reduction in disk I/O.

3-Reorganize tables to reduce disk I/O – This is done by selectively moving tables to tablespaces with a different blocksize, and re-sequencing table rows into the primary key