the DB Block size used, the higher the percentage of split blocks and the greater the potential for I/O performance degradation. When running Oracle 9i Release 2 (or later), it is possible to eliminate the 4k offset. This is recommended for new Oracle implementations or for existing applications with extremely high I/O performance requirements.
Currently, the capability to do this is delivered in two parts: An IBM AIX e-fix (APAR IY36656 for AIX 5.1) and an Oracle patch (bug 2620053). The functionality will be included in future release levels of AIX and in Oracle 9.2.0.3 or later. Once the prerequisite software has been installed, do the following to take advantage of the zero offset feature:
· Create a “big” Volume Group using the mkvg –B flag.
· Create one or more Logical Volumes in that Volume group using the mklv –T O flag. The “-TO” option indicates to Oracle that it can safely use a 0 offset for this Logical Volume.
In order to eliminate the 4k offset for an existing Oracle database, new Logical Volumes must be created and the existing data must be migrated to the new Logical Volumes using normal migration procedures.
This parameter is valid for RAC also. However, please make sure all the Database thread in RAC has the same offset/setup when using raw device for the redo log, as GoldenGate can't set specific RAWDEVICEOFFSET for each thread. This has to be across the board for all threads.