PDP-10 Archive: 4-documentation/mapper.tco from BB-J713A-BM

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TOPS20 Change Order Number 4.2569

Written by: DBELL		 9-Nov-79 10:37:37

Edit checked: NO			   Document: NO
  TCO Tested: NO		Maintenance Release: NO
Hardware-related: NO

Program: mapper

Related TCO's:
Related SPR's: 


Problem: 
Jobs can get unexplained "JFN not assigned" errors from various
programs if MAPPER is run in the job.

Diagnosis: 
Like many other programs that do this wrong, MAPPER does the following
sequence of JSYSes:  GTJFN, CFORK, GET, KFORK, and RJLFN.  Since the
GET JSYS releases the JFN (or hands it to the inferior fork), the final
RLJFN releases a JFN which is no longer valid, thus possibly destroying
a JFN that some other program had just obtained.

Solution: 
Don't do a RLJFN after the GET succeeds.