Mainframe, MVS and zOS Discussion

Hi,

Why browse is substituted if one tries to View/Edit a dataset with huge no. of records?

Can someone please explain.

TSO/ISPF edit requires memory. This memory is used to hold a copy of the entire data set to allow you to make changes to it. The changes are not committed to the data set until you use the SAVE command or exit the data set edit.

TSO/ISPF browse does not read the entire data set into memory. You can think of the browse screen as a window into the data set -- move the window and you'll see different records, but browse won't need much more memory than what is required to show one screen of records. For a large data set, if TSO/ISPF runs out of memory while attempting to edit the data set, browse is substituted to allow you to at least view the data records.

Is the region we see at Logon-ID have something to do here? I'm not sure but I vaguely recall that, such behaviour depends on that.

Yes, the region shown on the log on screen is the memory size allowed. There is some overhead with the system so if the value is 256000 then you cannot actually edit a file that contains 256,000 K of data.

Thanks Robert.

Robert Sample wrote:Yes, the region shown on the log on screen is the memory size allowed. There is some overhead with the system so if the value is 256000 then you cannot actually edit a file that contains 256,000 K of data.

Thanks Robert.

Is there any way using which we can change this size for a given session?

Thanks

Only if you have "powers" :-)

You'll need to talk to your support people, and explain why you need it. If you have a good case, and your boss behind you, you may get lucky. Generally, you can't "just do it" as it is system memory you are gobbling up, and if 50 developers all decide they "need" to do it...

Just to browse a large file is probably not a good reason. Use SORT to chop the file into smaller pieces and browse those (look at the SPLIT* options on OUTFIL).

You can change your maximum memory on the TSO signon screen. However, the value you put on this screen may be overridden by the site so just putting an arbitrary value there may not actually change anything. Furthermore, the value is setting the amount of memory your TSO session (that is, the address space) can use so you should NOT change the existing value without talking to your site support group first; setting the value incorrectly could cause various system problems.