Checklist #3: Writing an Exec that Sets up Allocation to SYSEXEC

Write an exec named SETUP that allocates data sets to SYSEXEC.
Create a data set member named SETUP in your exec PDS. In SETUP issue an ALLOCATE command that concatenates your PDS to the beginning of all the data sets already allocated to SYSEXEC. Include the data sets allocated to SYSEXEC from the list in the Preliminary Checklist. If there are no other data sets allocated to SYSEXEC, specify your PDS only. Your SETUP exec could look like the following example.
Sample SETUP Exec
```
/****************************** REXX *******************************/
/* This exec is an example of how to allocate a private PDS named  */
/* USERID.REXX.EXEC to the beginning of a concatenation to SYSEXEC */
/* that consists of one other data set named 'ISP.PHONE.EXEC'.  To */
/* make sure that SYSEXEC is available, the exec issues EXECUTIL   */
/* SEARCHDD(yes) command.  After the ALLOCATE command executes, a  */
/* message indicates whether the command was successful or not.    */
/*******************************************************************/
  "EXECUTIL SEARCHDD(yes)"   /* to ensure that SYSEXEC is available*/

  "ALLOC FILE(SYSEXEC) DATASET(rexx.exec,",
         "'isp.phone.exec') SHR REUSE"

  IF RC = 0 THEN
    SAY 'Allocation to SYSEXEC completed.'
  ELSE
    SAY 'Allocation to SYSEXEC failed.'
```
Note: The order in which you list data sets in an ALLOCATE command is the order in which they are concatenated and searched. To give your execs priority in the search order, list your data set of execs before other data sets.
Generally all the data sets in the list should have the same record format (either RECFM=VB or RECFM=FB) and logical record length, LRECL. Also, the first data set in the list can determine the block size, BLKSIZE, for the data sets that follow. If the block size of the first data set is smaller than the block sizes of subsequent data sets, you might end in error. To avoid error, use the Preliminary Checklist and the other checklists provided, and follow directions carefully.

Execute SETUP by entering the following EXEC command:

READY
EXEC rexx.exec(setup) exec

If the allocation was successful, you should then see displayed on your screen:

  Allocation to SYSEXEC completed.

To have SETUP execute when you log on and automatically allocate your data set to SYSEXEC, type the same EXEC command in the COMMAND field of your LOGON panel.

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