Creating and Managing Shadow Sets Using DCL
Commands
This chapter describes how to create, mount, dismount, and
dissolve shadow sets using interactive DCL commands. It also describes
how to use the DCL command SET DEVICE to specify management attributes for
shadow set members located at different sites in a multiple-site
OpenVMS Cluster system. In addition, it describes how to use the
DCL command SHOW DEVICE and the lexical function F$GETDVI to access current
information about the state of shadow sets.
Volume Shadowing for OpenVMS improves data availability by
ensuring that corresponding logical block numbers (LBNs) on multiple
disk volumes contain the same information. Upon receiving a command
to mount or dismount disks in a shadow set, the volume shadowing
software may need to reconcile data differences and ensure that
corresponding LBNs contain the same information.
An understanding of the copy and merge operations used for
data reconciliation is essential to the discussions in this chapter.
Therefore, you may find it helpful to refer to
Ensuring Shadow Set Consistency to understand how Volume Shadowing for OpenVMS
ensures data availability and consistency during changes in shadow
set membership.