Subhash,
To switch from dictionary-managed to locally managed tablespaces on existing
databases, a reorganization is necessary. Whether this reorganization can be done
online or must be done with export/import depends on the database version.
All tablespaces created by SAP installation tools in the "old" tablespace layout
were created as dictionary-managed tablespaces. SAP recommends using locally
managed tablespaces, which is standard if the new MCOD tablespace layout was
created by the installation tools.
In dictionary managed tablespaces, Oracle checks and updates data dictionary
tables whenever a new extent must be allocated (for example, due to table growth)
or deleted. The extent size and other parameters are called storage parameters
and are stored in the Oracle data dictionary.
Storage parameters can be set on the creation of a tablespace. These parameters
are then used for all tables in this tablespace as defaults. The defaults can be
overridden when a table is created, or changed with BR*Tools for existing tables.
With locally managed tablespaces, each data file has a bitmap listing used and
free blocks within the data file. When a new extent needs to be allocated, Oracle
selects one data file and checks in the bitmap, whether or not enough contiguous
blocks exist to create a new extent. It does so for each data file of the tablespace
until it finds the free space to allocate the extent.
For details check below mentioned SAP notes & links.
Note 214995 - Oracle locally-managed tablespaces in the SAP environment
Note 646681 - Reorganizing tables with BRSPACE
Note 541538 - FAQ: Reorganization
http://help.sap.com/erp2005_ehp_04/helpdata/DE/32/0d0c888839164ba4245b3ff7969c59/frameset.htm
Hope this answers your query.
Thanks
Sushil
Edited by: Sushil Suryawanshi on May 27, 2009 6:01 AM
Edited by: Sushil Suryawanshi on May 27, 2009 6:02 AM
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