Joined: 23 Nov 2006 Posts: 19270 Location: Inside the Matrix
Many systems migrate datasets based on last referenced date (rather than modified date). If you go into TSO 3.4 and place an "S" beside the files you want to keep online, they should not be migrated. If you do this weekly (unless your system migrates sooner) your files will be online.
You could also create a set of JCL that executes IEFBR14 and put in a DD statement for each dsn you want to keep online specifying DISP=OLD.
If you have not used the datasets for longer than the migrate time, why not let them migrate and then recall when you need it? Recall usually takes only a short time and does not need to tie up the terminal. Is there a good reason to have online dasd allocated for data that isn't currently being used?