Disk data sets

You can allocate a disk data set for use as an intermediate data file accessed by an IMS application program or any other user program. The operation is the same as for a tape file, but IMS provides no means of dismounting disk volumes.

When you allocate a group of disk data sets for the spooled SYSOUT option, the IMS Spool SYSOUT Print utility (DFSUPRT0) can copy one or more of these data sets to SYSOUT. IMS can automatically schedule this utility at end-of-volume on one of the data sets. An end-of-volume condition is also simulated:

• If an I/O error occurs while writing to a spool data set.
• During system initialization, if a spool data set was in use when the system was last running and the spool data set was not printed.

  In this case, you must issue a /START LINE command to complete the scheduling procedure.

  Recommendation: Define at least two data sets for your spool line.

You can reschedule the utility with the /STOP LINE PTERM command. You can also start the utility at any time by issuing a /START REGION procname command from the master terminal. IMS generates line numbers and PTERMs in the sequence of the input definition statements during IMS system definition. After the system is generated and ready to run, you can display line numbers to determine what line number was generated for a spool data set.

You must establish your own conventions for controlling special forms. One possible method is to allocate a logical terminal for each report. After you set up the forms for a specific report, lock the other logical terminals using the /LOCK LTERM command, then place the terminal in exclusive mode using the /EXCLUSIVE command. Thereafter, IMS prints only the data enqueued for the report you want. If you do not use a technique like this one, messages alternate among the logical terminals associated with the line.