Metro Mirror test scenario: failback operation from local to remote site

This scenario describes the steps required to test the failover and failback procedures in which a failback is done from the local site to the remote site. This test allows you to bring up a test application on the remote volumes. Then, after the test is complete, resynchronize the remote volumes from the local (production) volumes by copying only changed tracks.

Assume the following for this scenario:

Production is running at Site A (the local site).
You have simulated a disaster by disabling the links between the local and remote storage units.

Complete these steps for the failover and failback test scenario. (The parameters and values included in this scenario are examples.)

Freeze updates to the primary (A) volumes in Metro Mirror relationships across the affected LSSs. This process ensures that the secondary (B) volumes will be consistent at the time of the freeze. (One command per LSS is required.) Enter the freezepprc command at the dscli command prompt with the following parameters and variables:
```
freezepprc -dev IBM.2107-130165X -remotedev IBM.2107-75ALA2P 07:12
```
The following represents an example of the output:
```
CMUC00161W freezepprc: Remote Mirror and Copy consistency group 07:12 
successfully created.
```
As a result of the freeze action, the following processing occurs:
- I/O processing to the Metro Mirror volume pairs is temporarily queued during the time that updates are frozen.
- The volume pairs that are associated with the source and target LSSs are suspended. During this time, updates are collected using the change recording feature on the Site A volumes.
- The established paths between the LSS pairs are disabled.
Resume operations following a freeze.
Issue the unfreezepprc command to allow I/O activity to resume for the specified volume pairs. Enter the unfreezepprc command at the dscli command prompt with the following parameters and variables:
Note: This action is sometimes referred to as a thaw operation.
```
dscli> unfreezepprc -dev IBM.2107-130165X -remotedev IBM.2107-75ALA2P 07:12 
```
The following represents an example of the output:
```
CMUC00198I unfreezepprc: Remote Mirror and Copy pair 07:12 successfully thawed.
```
At Site B (remote site), issue a failover command to the B to A volume pairs. Enter the failoverpprc command at the dscli command prompt with the following parameters and variables:
```
dscli> failoverpprc -dev IBM.2107-75ALA2P -remotedev IBM.2107-130165X -type
mmir 1200-125f:1a00-1a5f
```
The following represents an example of the output:
```
CMUC00196I failoverpprc: Remote Mirror and Copy pair 1200:1A00 
successfully reversed.
CMUC00196I failoverpprc: Remote Mirror and Copy pair 1201:1A01
 successfully reversed.
```
When this command processes, the following occurs:
- The B volumes become suspended primary volumes. Updates are collected using the change recording feature on the volumes.
- The A volumes are suspended primary volumes.
Allow test I/O to start at Site B.
When testing is complete, perform the following steps:
1. Quiesce test I/O at Site B (remote site).
2. Enable the remote mirror and copy links between the storage units across the two sites. (The paths will not reestablish automatically.)
3. Reestablish paths between the local and remote site LSSs that contain the Metro Mirror volume pairs. Enter the mkpprcpath command at the dscli command prompt with the following parameters and variables:
```
dscli> mkpprcpath -dev IBM.2107-130165X -remotedev IBM.2107-75ALA2P 
-remotewwnn 5005076303FFC550 -srclss 07 -tgtlss 12 -consistgrp 
I0102:I0031 I0002:I0102 
```
  The following represents an example of the output:
```
CMUC00149I mkpprcpath: Remote Mirror and Copy path 07:12 
successfully established.
```
At the local site, issue a failback command to the A to B volume pairs. Enter the failbackpprc command at the dscli command prompt with the following parameters and variables
```
dscli> failbackpprc -dev IBM.2107-130165X -remotedev IBM.2107-75ALA2P  
-type mmir 1a00-1a5f:1200-125f
```
The following represents an example of the output:
```
CMUC00197I failbackpprc: Remote Mirror and Copy pair 1200:1A00 
successfully failed back.
CMUC00197I failbackpprc: Remote Mirror and Copy pair 1201:1A01 
successfully failed back.
```
When this command processes, the following occurs:
- Updates that are made to the volumes at Site B are recorded with the change recording feature. Changed tracks of data are copied from the Site A volumes to Site B volumes.
- When the copy process is complete, the Site A volumes will be synchronized with the Site B volumes.
Production I/O continues to the A volumes.