Mainframe Enablers TimeFinder SnapVX and zDP 8.5 Product Guide

If a device is specified as a copy-once device, it is included only in the first snapset that is created after the start of a VDG.

If a device is dynamically added to the VDG as a copy-once device, zDP creates a saved snapset for all devices in the VDG, including the newly added copy-once device. If all devices in a VDG are defined as copy-once devices, the VDG stops after the first cycle.

The Copy Once feature can be used, for example, when you want to include the system volumes in a snapset for recovery purposes, but the data on a page volume is not useful or needed for recovery. Page, dump, and sysres volumes are good examples to use this feature.

A copy-once snapset is created as a saved snapset, with no expiration time. The Copy Once attribute takes precedence over the Secure attribute (a secure snapset must have an expiration time).

Copy-once snapsets have the persistent attribute and are included in the PERSISTENT_COPY_LIMIT count.

The zDP Definition Utility allows you to define copy-once devices, view copy-once devices and snapsets, and control inclusion of copy-once devices in LINK or RESTORE operations.

Defining copy-once devices

To set the copy-once attribute for the devices, specify the COPY_ONCE keyword on the MODIFY VDG,ADD statement.

Viewing copy-once devices and snapsets

In the QUERY VDG,DEVICE report, copy-once devices are indicated with /O following the device number:

EIP0027I      CCUU    DEVICE    TYPE     SIZE     SRP ID   RDF INFO/MODE 
EIP0027I      ____    ______    ____   ________   ______   ______________
                                                                         
EIP0028I      3150    000170/O   CKD      32760    0001    --- 
...

To view the last snapset that includes a copy-once device, specify the COPY_ONCE option on the QUERY VDG,DEVICE command. The snapset is displayed in the COPY_ONCE SSET field:

EIP0027I      CCUU    DEVICE    TYPE     SIZE     SRP ID   RDF INFO/MODE    COPY_ONCE SSET
EIP0027I      ____    ______    ____   ________   ______   ______________   ______________
                                                                          
EIP0028I      3150    000170/O   CKD      32760    0001    ---              171360952S00001

To view a list of snapsets that contain copy-once devices defined in the current VDG, issue the QUERY VDG,SNAPSET command with the COPY_ONCE option. The copy-once filter is indicated with ‘(COPY_ONCE)’ in the query heading:

EIP0035I   Snapset Query for VDG EMCVDGC1 (COPY_ONCE)

Linking and restoring copy-once devices

To include copy-once devices for a LINK or RESTORE of a snapset that does not contain the copy-once devices, specify COPY_ONCE(INCLUDE) on the LINK or RESTORE command.

To manually link or restore the copy-once devices from a specific snapset, specify COPY_ONCE(ONLY) on the LINK or RESTORE command.

Unlinking copy-once devices

An UNLINK for a linked snapset unlinks all devices (including copy-once devices). However, because a target set is not employed for RESTORE, an UNLINK for a restored snapset unlinks only the devices in the specific snapset. A separate UNLINK command for the snapset containing the copy-once devices must be issued.