Using fast reverse restore processing to create consistency

Complete this task to create the same consistent data on the B volumes that you have on the C volumes. The fast reverse restore option allows you to reverse a FlashCopy® relationship without waiting for the background copy of a previous FlashCopy operation to finish. This is the sixth step in the Global Mirror disaster recovery process.

About this task

The fast reverse restore option reverses a FlashCopy target volume and allows consistent data to be copied back to its associated source volume, without having to wait for the background copy from the original source to the original target to complete. You can then vary the volumes online and start your applications.

Fast reverse restore processing creates a background copy of all tracks that changed on the B volume since the last consistency group formation. This results in the B volume becoming the same as the image that was present on the C volume. However, this process ends the FlashCopy relationship, so that the C volume is no longer usable.

Use the DS CLI reverseflash command with the -fast parameter to accomplish this task. This command results the following conditions:
  • Start background copy from the C volumes to the B volumes.
  • No change recording.
  • There must be no I/O allowed to the B or C volumes during the fast reverse restore process.

Complete the following step to create the same consistent data on the B volumes that you have on the C volumes. The example command in this task is shown in two formats. The first format shows the type of information that the command requires. The second format provides the command with declared values for the variables.

Note: You can issue the command that is described in the steps below either for a DS8000® model or for a DS6000™ model, but for the DS6000 model the storage image ID is different.

Procedure

Issue the reverseflash command to create the same consistency on the B volumes that you have on the C volumes. Enter the reverseflash command at the dscli command prompt with the following parameters and variables:

dscli> reverseflash -dev storage_image_ID -fast -tgtpprc source_volume_ID:target_volume_ID

Example

dscli> reverseflash -dev IBM.2107-75FA150 -fast -tgtpprc
0200:0100
Notes:
  1. The -fast parameter determines that the reverseflash command is processed before the background copy completes.
  2. When you reverse a FlashCopy relationship, the source and target IDs that you specify for the reverseflash command must be the same as the source and target IDs from the original FlashCopy relationship (the source and target IDs from the relationship before it is reversed). The target volume ID is the value that is specified for the C volume. The data from this volume is copied back to the source volume ID, which is the B volume.
  3. The -tgtpprc parameter allows the FlashCopy target volume (B volume) to be a Remote Mirror and Copy source volume.
  4. The storage_image_ID parameter is the value that is assigned to the remote storage unit, which has become the primary storage unit as a result of the failover action.
  5. You must wait for the background copy to complete before you can proceed to the next process.