Steps for using P/DAS in a sysplex environment

In the sysplex environment, P/DAS operations are similar to those of the nonsysplex, shared-disk environment. See P/DAS operations example for an example of a sysplex scenario.

Before you begin:

You must choose one system to be the "main system." When multiple systems are involved, you must issue the following commands on each system in the specified order.
If volume pairs are in PPRC extended distance mode, convert the pairs to synchronous mode to allow them to reach DUPLEX status before a swap operation begins. This ensures that the volume pairs are in sync and all updates are copied to the secondary.

Perform the following steps to use P/DAS in a sysplex environment:

Issue ROUTE *ALL,IOACTION STOP,DEV=ssss.
Initiate a P/DAS operation by issuing this command on the "main system." This command requests that P/DAS stop I/O that is directed to device number ssss. ROUTE *ALL directs this action to all systems in the sysplex. DEV=ssss specifies a primary volume of a duplex PPRC volume pair. The MVS system stores all application I/O that is issued to the primary volume until you issue a ROUTE *ALL,IOACTION RESUME command. P/DAS ends, with a simulated I/O error, any active I/O that does not complete within five seconds after MVS has accepted the IOACTION STOP. This action forces the disk error recovery procedures to retry the I/O operation.
The MVS system issues the following messages to the operator console for all systems in the sysplex when the I/O for the primary device has been stopped on that system:
```
IOS600I IOACTION - THE FOLLOWING DEVICE(S) HAVE BEEN STOPPED:
                   dev dev1-dev2...
 
   IOS601I IOACTION - DEVICES REMAIN IN THE STOPPED STATE.
           USE THE 'D IOS,STOP' COMMAND TO DISPLAY THE DEVICES
```
When all attached systems have received these messages, continue with the SWAP command. MVS issues an IOS610I message in response to your D IOS,STOP command.
Issue ROUTE *ALL,SWAP ssss,tttt.
Issue the ROUTE *ALL,SWAP command for the volume pairs involved in the P/DAS operation. ROUTE *ALL automatically directs this action to all systems in the sysplex. This command directs the systems to switch the source device ssss with the target device tttt, and prepares the systems to redirect all I/Os issued to device ssss to the target device tttt.
P/DAS performs validation.
Before the SWAP operation is complete, P/DAS performs validation to ensure that it can complete the swap operation. If conditions exist that can cause a data integrity exposure, P/DAS ends the operation and generates an error message. See P/DAS error conditions for error message descriptions.

P/DAS does not proceed when it cannot determine the status of both volumes, or when the volumes are not in duplex state. Ensure that the environment meets the conditions that are necessary to support P/DAS. Preparing for P/DAS operations describes the conditions.
If the validation completes successfully, P/DAS issues the following message to prompt the operator as to how to proceed:
```
IGF520A VERIFICATION COMPLETE: REPLY 1 TERMINATE PAIR, AND SWAP
    │ 2 SWITCH PAIR, AND SWAP │ 3 CONTINUE SWAP │ 4 TERMINATE SWAP
```
Select the P/DAS action.
Attention: Do not reply to any of the system messages until all of the systems in the sysplex have issued IGF520A messages.
Select one of the following replies from the main system console:
- Reply with "1" to end the pair and redirect I/O to the secondary volume.
- Reply with "2" to swap the primary and secondary volumes and redirect all I/O to the new primary volume.
Attention: If more than one system issues the reply from the main system console, the P/DAS swap operation may fail on one or more systems. If such an error does occur, reestablish the PPRC pair on all systems and retry the P/DAS operation.

If you choose Reply 2 (switch pair, and swap), P/DAS directs the system to take action according to the PPRC environment that is in effect at the time the command is issued, as described in Table 1.
The main system issues the following completion message when the swap function is complete:
```
IGF505I SWAP FROM ssss TO tttt COMPLETE 
```
Variable ssss is the source device number, and tttt is the target device number.
Reply from other sysplex systems.
Ensure that the main system has issued an IGF505I message before replying to outstanding IGF520A messages on other sysplex systems. At this point, reply to outstanding IGF520A messages on all other sysplex systems by entering "3" (Continue Swap). Table 1 describes the resulting system action.
Issue ROUTE *ALL,IOACTION RESUME,DEV=tttt.
Each of the attached sysplex systems issues an IGF505I message in response to your "Continue Swap" reply. Ensure that all systems in the sysplex have received the IGF505I message, and then issue the IOACTION RESUME command to device number tttt. You must issue the command to device number tttt because device tttt is now the primary volume. The IOACTION RESUME command resumes all application I/O to device tttt. All application I/O that used to go to the source device ssss now goes to the target device tttt instead.

This command is equivalent to the IOACTION RESUME command in the nonsysplex, shared-disk environment. The difference is that the specification of ROUTE *ALL directs this action to all systems in the sysplex. Every system in the sysplex should acknowledge this command with an IOS607I message.
Note: P/DAS does not actually redirect and resume the application I/O to the target volume until this step has completed. Each attached system redirects the I/O as it receives and processes the IOACTION RESUME command.