If you are a little interested in MVS it is hard to ignore a tool like SDSF. SDSF can show you a lot of information about what is going on right now in your MVS system. SDSF has an additional feature that allows you to see address space activity for other MVS systems than the one that you are currently logged on to in the Display Active (DA).

The command that enables this feature is called SYSNAME. You must be authorized to use it and your SDSF and MVS must support the feature. My guess is that most installations have been upgraded to the version of SDSF and MVS that supports SYSNAME. When you enter the DA display you will se the address spaces of the MVS that you are logged on to by default. In the upper let corner you see the name of the MVS system you are logged on to and to the right of this field is another field telling you the name of the MVS that is displayed in DA. Until I discovered the SYSNAME command I was irritated by the fact that these two fields always showed the same contens.

The command SYSNAME * allows the DA display to show address spaces from all MVS systems in the SYSPLEX. After a SYSNAME * you can issue a PREFIX CATALOG. In this way you will se how many MVS systems there are in the SYSPLEX and if you find the corresponding column in the DA display you can see the names of all the different MVS systems.

Now you are able to select a certain MVS system that you want to monitor using the command SYSNAME <mvs> where <mvs> is the name of the MVS you want to view in DA. When you want DA to view only the MVS that you are logged on to then you issue a SYSNAME without parameters. Another way to return to default DA view is to look in the upper left corner and use this MVS system name as parameter to the SYSNAME command. The result is the same but the latter is a bit longer.