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Chapter 5. Problem Determination, Diagnostics, and Recovery 385
1st ed., 6/30/04 - 312579601
CDS Recovery Capabilities
Capabilities to recover the CDS from certain hardware and software failures are inherent
in the HSC. CDS recovery capabilities include:
• dynamic recovery of the control data set
• control data set error diagnostics
• initializing/running on one copy of the control data set
• switching to another copy of the control data set
• control data set integrity during BACKup and RESTore
• detecting mismatch of control data sets
Additional recovery information is available in the HSC Operator’s Guide pertaining to
the following topics:
• cartridge recovery
• errant cartridge recovery
• switch to standby LMU
• automatic downward switch of the host-to-host communication method level
• starting the HSC at the base service level
Control Data Set Recovery
Dynamic Recovery of the Control Data Set
At HSC installation, specifying additional control data sets, secondary and standby, in the
LIBGEN SLIRCVRY macro indicates that these additional copies of the control data set
are maintained by the HSC during library operation and kept on DASD. In addition, a CDs
operator command provides you with the capability to enable or disable any of the various
control data sets. An auto-enable function of the command sets the automatic switch
capability of the HSC to automatically switch operation to another control data set.
If a failure occurs accessing the primary control data set, the HSC automatically switches
operation to the secondary control data set. At the time that the switch to the secondary
control data set occurs, the standby control data set becomes valid. After library operation
continues with the secondary control data set, should the secondary control data set
become inaccessible, the standby control data set is accessed and used by the HSC to keep
the library operating.
Note: If the primary and secondary control data sets fail simultaneously, without sufficient
time for the HSC to make the standby data set valid and accessible, HSC operation is
impaired.
These backup data sets replace a failing control data set; however, they retain their original
data set name.