Siebel Server Installation Guide for Microsoft Windows > Creating the Oracle Database > Planning the Distribution of Your Database Objects >

Mirroring Important Oracle Files

Many companies today use RAID storage systems that make Oracle online redo log mirroring unnecessary.

If your organization does not use RAID storage systems, you should, at a minimum, mirror the redo log, as this is essential when a database goes through crash-recovery.

Also, when redo logs are mirrored at the RAID storage system level (usually RAID1 or RAID0+1), there is usually no need to mirror them at the Oracle level, since the RAID controller assures that these volumes can always be recovered. Mirroring at the RAID level usually improves database performance (especially beneficial for read operation).

If you have the resources, the Oracle control files should be mirrored as well. Otherwise, you can put the Oracle control files into a RAID-5 device as it is not heavily accessed and disk performance is not a concern. The information it records, though, is very critical for the Oracle database. Any updates to the control file—for example, the current System Change Number (SCN) or transaction tables—ripple across all members of the control file specification.

NOTE:  For data that is accessed heavily, disk subsystem mirroring (hardware mirroring) generally provides better performance compared to RAID5.

 Siebel Server Installation Guide for Microsoft Windows 
 Published: 25 June 2003