Restoring an original unit

Within a snap session, the original unit of a snap pair can be reconstructed by copying the data from the snap unit to the original unit. This reconstruction can be started for all snap pairs of a pubset or for individual snap pairs. Reconstruction results in all modifications which were made on the original unit after the snap unit was activated being discarded.

Requirements

• Processing on the original unit and snap unit has been terminated.

• Original pubsets and the snap pubset have been exported, provided all original units of a pubset are to be reconstructed.

• Only relevant for Symmetrix: when multiple snap sessions exist for the same original unit, all of these are in the COPY-ON-WRITE or COPIED status, i.e. no snap session for the original unit is in the CREATED or RESTORED status.

• Only relevant for Symmetrix: No clone session exists for the original unit.

Initiating reconstruction

Copy the data to the original units using the /RESTORE-FROM-SNAP command (see "RESTORE-FROM-SNAP Reconstructs an original from a snap unit"):

/RESTORE-FROM-SNAP 
   UNIT=*BY-PUBSET(PUBSET=<cat-id>) / *BY-VOLUME(<vsn>) / <unit MN> /...

Further sequence of operations

ETERNUS DX/AF

• After reconstruction snap sessions are in the COPY-ON-WRITE status and accessible.

• The snap pairs can still be used. Further reconstructions can also be started.

• For ETERNUS DX/AF, asynchronous reconstruction after command execution or synchronous reconstruction during command execution is possible (WAIT operand). The snap pair is in the REST-IN-PROG status during synchronous reconstruction. Waiting can be aborted in dialog mode by hitting the K2 key.

• The /STOP-SNAP-SESSION and /START-SNAP-SESSION commands are rejected with return code NDE1820 while reconstruction is being performed. They can only be executed successfully after reconstruction has been completed.

• Reconstruction is not possible if the original unit is also a clone unit.

Symmetrix

• During the copy process the snap pairs are in the REST-IN-PROG status, and after termination in the RESTORED status. The message NDE0050 indicates these statuses.

• Snap units are not accessible after reconstruction has taken place.

• A snap pair in the RESTORED status can no longer be used and should be canceled. This is particularly true when multiple snap pairs were created for a original unit or a new clone pair is to be created with the original unit.

• Other snap statuses can also be reconstructed.

• The WAIT=*NO operand in /RESTORE-FROM-SNAP defines that the command is not waiting for reconstruction to terminate (asynchronous command execution).

• The WAIT=*UNTIL-RESTORED operand in /RESTORE-FROM-SNAP defines that the command will wait for reconstruction to terminate (synchronous command execution), i.e. until the snap pair is in the RESTORED or COPY-ON-WRITE status. In interactive mode, the wait status can be aborted by hitting the K2 key.

VMAX3

• After reconstruction snap sessions are in the COPY-ON-WRITE status and accessible.

• The snap pairs can still be used. Further reconstructions can also be started.

• Reconstruction itself is always executed synchronously in the VMAX3. It cannot be monitored from the outside.