Advanced Topics › Configure CTCPATH Statements for Disaster Recovery

Configure CTCPATH Statements for Disaster Recovery

Some data centers want to IPL a given system on two different CPUs. For example, consider a MIMplex with three systems – GK03, GK13, and GK62.

• CPU1 contains GK03 and GK13
• CPU2 contains GK62.

However, if CPU1 fails, then you start GK03 and GK13 on CPU2. Conversely, if CPU2 fails, then start GK62 on CPU1.

The client can code all necessary CTC device addresses in any order, as long as COMPATLEVEL=12.0 or higher.

Follow these steps:

1. Code the CTC device addresses on a single CTCPATH statement.

   CTCPATH FROMSYS=GK03 TOSYS=GK13 ADDR=(183A,154A,B3A,C3A)
   CTCPATH FROMSYS=GK03 TOSYS=GK62 ADDR=(184A,180A,B4A,C4A)
   
   CTCPATH FROMSYS=GK13 TOSYS=GK03 ADDR=(183A,154A,B3A,C3A)
   CTCPATH FROMSYS=GK13 TOSYS=GK62 ADDR=(187A,BFA,B7A,C7A)
   
   CTCPATH FROMSYS=GK62 TOSYS=GK03 ADDR=(184A,180A,B4A,C4A)
   CTCPATH FROMSYS=GK62 TOSYS=GK13 ADDR=(187A,BFA,B7A,C7A)
   

2. Review the CTCPATH statement between GK03 and GK62.
   • The first two addresses(184A,180A) are used when GK03 is on CPU1.
   • The remaining two(B4A,C4A) are used when GK03 is started on CPU2.

   The same is true for the CTCPATH statement between GK62 and GK03.

   • The first two addresses(184A,180A) are used when GK03 is on CPU2.
   • The remaining two(B4A,C4A) are used when GK03 is started on CPU1.
3. Code the CTC devices in any order.

   CTCPATH FROMSYS=GK03 TOSYS=GK62 ADDR=(184A,180A,B4A,C4A)
   CTCPATH FROMSYS=GK62 TOSYS=GK03 ADDR=(C4A,B4A,180A,184A)
   

As you can see, device #1 on GK03 is connected to device #4 on GK62. You can code the CTC devices in any order.