If you ever programmed an ISPF application you have encountered at least one socalled Z variable. All variable names in ISPF are limited to a maximum length of 8 characters and you should not use Z as the first character. Z is reserved for predefined variables in ISPF. There are Z variables for dates, for some ISPF services and for system information. There are two appendices in ISPF for z/OS version 1 release 8, one about dialog variables and the other about system variables. In these two appendices all Z variables are quite nicely documented.

If you want to see the current contents of the Z variables that ISPF predefines for you it is surprisingly easy. Please choose item 7 Dialogue Test on the ISPF standard main menu. On the menu for Dialogue Test you must choose item 3 Variables. This will display a list of all variables known to ISPF for the active APPLID. Because predefined Z variables are common to all APPLIDs it does not make any difference which APPLID is active, but there may be a long list of other variables which does not start with Z and the names and numbers of these variable may vary significantly from APPLID to APPLID.

You are able to browse the list of variables in the usual ISPF fashion. Please note that non-modifyable Z variables are on top of the list, while you might have to browse forward in order to list the modifyable ones. Some of the Z variables I am fond of are ZISPFOS and ZOS390RL, which contains information about current ISPF release and z/OS release. One the installation where I currently work they change z/OS release quite often and some of the MVS systems are not using the same z/OS release. In those cases it is nice to known that such information is available in ISPF Z variables and that it is easy to display the contents of the Z variables using Dialogue Test.

If you are looking for the contents of a Z variable, you know the name of, you can use the command L <Z-variablename> and you may even use just part of the name and use RFIND (F5) to find the next matching name in the list. Well, why then use LOCATE as command name instead of FIND. Sometimes IBM works in mysterious ways.