P/DAS operations example

Table 1 shows the sequence of events that make up a P/DAS operation in a sysplex environment. As in all P/DAS operations, the correct command sequence is necessary to perform a successful P/DAS exchange of devices.

In this example, there are three systems in the sysplex that share volumes 191 and 581. System A is the main system and has the master console. Initialize the environment by establishing a single-direction PPRC path from the storage control for device 191 to the storage control for device 581. Device 191 is the primary volume of the PPRC pair, and device 581 is the secondary volume.

Note: 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.

In preparation for P/DAS operation, the storage administrator issues two CESTPAIR commands. The commands are issued:

From any of the attached systems to establish a path from the storage control for device 191 to the storage control for device 581.
From any of the attached systems for device 191 (primary) and device 581 (secondary). PPRC copies all of the tracks on device 191 onto device 581.

Table 1 shows what happens when the P/DAS operation begins.

Table 1. Example of a P/DAS swap function in a sysplex environment
System A (main system)	System B	System C
Operator issues: ROUTE *ALL,IOACTION STOP,DEV=191. System A stops I/O on 191, then issues IOS600I and IOS601I messages.	System B stops I/O on 191, then issues IOS600I and IOS601I messages.	System C stops I/O on 191, then issues IOS600I and IOS601I messages.
Operator issues: ROUTE *ALL,SWAP 191,581. System A performs validation, then issues IGF520A message.	System B performs validation, then issues IGF520A message.	System C performs validation, then issues IGF520A message.
Operator issues: R nn,1. System A ends PPRC pair, swaps pair, then issues IGF505I message.	After IGF505I message received, operator issues: R nn,3. System B swaps PPRC pair, then issues IGF505I message.	After IGF505I message received, operator issues: R nn,3. System C swaps PPRC pair, then issues IGF505I message.
Operator issues: ROUTE *ALL,IOACTION RESUME, DEV=581. System A directs I/O to 581, then issues IOS607I message.	System B directs I/O to 581, then issues IOS607I message.	System C directs I/O to 581, then issues IOS607I message.