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Chapter 2. Host Software Component Functions 59
1st ed., 6/30/04 - 312579601
Control data sets can be accessed by different hosts and are kept synchronized. In event of
a failure, the BACKup and RESTore utilities can be used to perform extensive error
checking and synchronization of the data. A backup control data set and journals are used
to reconstruct the control data sets.
The integrity of the control data sets is extremely important. In multiple processor
environments, data set integrity is much more difficult to maintain. Because of this, the
HSC subsystem is designed to keep the control data sets intact and configured to recover
from failures. Features such as shadowing for the control data set, journaling, backup and
restore were previously in place in prior releases to maintain data set integrity.
Control Data Set Recovery Techniques
There are several techniques to accomplish control data set recovery. These techniques
are:
• dynamic recovery of CDS errors (when possible)
- switch
- internal CDS directory rebuild
- standby CDS copy.
• diagnostic information on CDS errors, error detection, and correction of the CDS
through the BACKup and RESTore utilities
• the ability of the HSC to continue running on one copy of the CDS
• user control of enabling and disabling control data sets with operator commands
• automatic communication with other hosts in a complex when control is switched
from one CDS to another.
User Control of Control Data Sets
The HSC offers flexibility for definition and control of control data sets. User control of
these data sets includes:
• allocation of data sets at initialization
• ability to dynamically enable or disable the library control data sets
• reassigning control data set names in the Database Heartbeat record.
Allocation of Control Data Sets
Control data sets are defined at HSC initialization by PARMLIB control statements rather
than defined by JCL. These definitions are invoked at HSC initialization and remain set
until HSC termination. The definitions cannot be altered without HSC shutdown and
restart.
Refer to “PARMLIB Control Statements” on page 67 for detailed information about
PARMLIB control statements.