StorageTek 6 manual Near Continuous Operations, Using Multiple CDS Copies

Near Continuous Operations

A number of HSC facilities and techniques are provided that customers can employ to avoid outages and make changes less disruptive to their library hardware and HSC environment.

This section discusses the following topics:

•using multiple CDS copies

•automatic recognition of configuration changes

•using the SET utility instead of LIBGEN and reconfiguration

•defining a new configuration to avoid future reconfigurations

•defining planned ACSs with no stations

•changing panels

•using CDS rename/relocate/expand.

In addition, several other timesaving benefits are described in other places in the HSC documentation set. These are:

•converting the CDS level from 2.0 to 2.1 while HSC 2.0.1 remains active. Refer to the HSC Installation Guide, ‘‘CDS Conversion Requirements (Up-Level Migration),’’ in Appendix D, ‘‘Migration and Coexistence Processes.’’

•resolving LSM and panel type configuration mismatches. Refer to either the HSC Installation Guide, ‘‘Configuration Mismatches,’’ in Chapter 8, ‘‘HSC Initialization’’ or see the HSC System Programmer’s Guide, “Configuration Mismatches” on page 163.

•changing drive panel types without running a reconfiguration. Refer to the HSC System Programmer’s Guide, “SET Device Numbers for Drives” on page 405.

•automatic internal cold start for HSC 2.0.1 and later releases. Refer to either the HSC Installation Guide, ‘‘Starting HSC Execution’’ in Chapter 7, ‘‘Initializing the HSC’’ or see the HSC System Programmer’s Guide, “Starting HSC Execution” on page 225.

•suppressing the ‘‘ACS Disconnected’’ message to allow for future hardware expansion. Refer to the HSC Operator’s Guide, ‘‘OPTION Command and Control Statement,’’ in Chapter 2, ‘‘Commands, Control Statements, and Utilities.’’

Using Multiple CDS Copies

When multiple copies of the CDS are defined and enabled, the HSC automatically recovers from errors on one of these copies. In a multiple-host environment, CDS recovery is coordinated among the HSCs on all hosts.

•When there is a mismatch between information on the same block on the primary and secondary CDS copy, the HSC automatically selects the most recent copy. When the CDS is updated, the modified block is written to both the primary and secondary CDS copies.

•If a secondary CDS copy is active, and a failure occurs in accessing the current primary CDS copy, the HSC automatically makes the secondary CDS copy the

Chapter 2. Host Software Component Functions 49

1st ed., 6/30/04 - 312579601