OSE Processing

As each data set is selected, a temporary OSE is constructed containing all scheduling requirements. A call is then made to installation exit IATUX19 to allow the system programmer to examine and, if required, to change the information before the OSE is spooled. For SYSOUT destined for a BSC/NJE or SNA/NJE destination, changes to characteristics must be made in IATUX39.

When control is returned from the installation exit, if the OSE copy count is nonzero, the OSE is added to the job's OSE spool file. Then, the master OSE (MOSE) pool, which is in main storage, is searched. If an identical master OSE is found, an output scheduling summary (OSS) entry is chained onto that master OSE. If no identical master OSE is found, a new master OSE is created and an OSS is also created, chained to the new MOSE, and added to the pool.

After all the above processing for the current job has completed, the queueing function posts the start writer function to determine which jobs are eligible for writer scheduling. The start writer function tries to associate each master OSE of a job with a SAPI application, an external writer, an output device or with an active writer that is waiting for more work.

The following rules apply:

When a SYSOUT initialization statement uses an output descriptor (direct or default) that is defined through an OUTPUT JCL statement or a TSO OUTDES command, JES3 uses the values from that output descriptor, the SYSOUT initialization statement, and the OUTSERV initialization statement to establish the output characteristics of the data set.
The characteristics that are defined in the output descriptor override any duplicate characteristics of the SYSOUT initialization statement. The characteristics of the SYSOUT initialization statement override any duplicate characteristics of the OUTSERV initialization statement.
When a TSO user issues the TSO OUTDES command to define a default output descriptor, any SYSOUT the TSO user creates is associated with that output descriptor.
- Given the following initialization statements:
```
OUTSERV,COPIES=1
SYSOUT,CLASS=B,TYPE=PUNCH,COPIES=2
```
  If the TSO user issues the TSO TRANSMIT command, then only one copy of the data set is sent.
  If the TSO user issues the TSO OUTDES xxxx ... DEFAULT command followed by a TSO TRANSMIT command, two copies of the data set are sent.
  TSO OUTDES Command:
```
OUTDES MYOUTDES DEFAULT NAME('My Name')
```
  The COPIES=2 parameter from the SYSOUT initialization statement merges into the SYSOUT characteristics because the SYSOUT is associated with an output descriptor that is created by the OUTDES command.
- If there are more than one default //*FORMAT statements for the same data set, JES3 merges the information from them. JES3 lets parameters that are specified by later default //*FORMAT statements to override those specified by earlier default //*FORMAT statements. The user receives the data set formatted only one way.
- If both direct OUTPUT JCL statements and direct //*FORMAT JES3 control statements apply to the same data set, JES3 formats the data set according to the specifications of each direct OUTPUT JCL statement and each direct //*FORMAT JES3 control statement. That is, JES3 creates a separate OSE for each OUTPUT JCL statement and each direct //*FORMAT JES3 control statement. Each OSE results in a formatted version of the data set so that there are as many formatted versions of the data set as there are direct OUTPUT JCL statements and direct //*FORMAT JES3 control statements for that data set.
After a piece of sysout is created, if it is changed to a new class, then the characteristics of the new class (that were not explicitly specified on a statement, such as DD, which would override the SYSOUT initialization statement) are applied to the sysout. The DSISO, SPART, and OUTDISP attributes of the new class are not applied to the sysout.