>Abi Admassu asks:
>
>> We are running ADSM V1R1L12 on MVS.  Our mainframe group recently moved the
>> recovery log and the server databse to RAMAC.  Is there any need for
>> mirroring the database and recovery log if both are on RAMAC?  Other than
>> sudden power outages, what other scenarios corrupt the database?  Any input
>> is greatly appreciated.
>
>The purpose of mirroring the database and log is for protection against media
>failures (i.e. head crashes). Mirroring the database does *not* protect
>against corruption. By "corruption", I mean a *logical* failure in the data
>(broken pointers, invalid data values, etc.). An incorrect record written to
>one copy will also be written to the other copy, so the mirroring is of no
>help against corruption.
>
>This being the case, any fault tolerant device should protect you from media
>failures, and your database should be as safe on it with one copy as it
>would be on traditional (non-fault tolerant) DASD with two copies.
>
>Andy Raibeck
>Connecticut Mutual
>203-987-3521
>


Thanks for taking time to answer my questions.  I guess  maybe the one
instance where mirroring protects against corruption is if ever a partial
write occurs, for example during a power outage, and corrupts the recovery
log, restarting the server using a mirrored recovery log can be used to
build the missing pages.

Abi