++APAR(ASZ3222). /*-----------------------------------------------------

COPYRIGHT AUSTRALIAN SYSTEMS ENGINEERING PTY. LTD. 2001.

ASZ3222 010726 61VTEL JB ASEB200 V201 WAIT       ASEDAMGR ...... 0911PMD
TSO user locks up ASEDA... resource for .JOBDETL MASTER after *** wait

_PROBLEM DESCRIPTION:
TSO user waiting to open an OMCS database file is in "output wait" state
with "***" on the screen.  TIOC is waiting for the user to press ENTER
or CLEAR.  Other address spaces are waiting to open the same database
file and are issuing the DAIO45I message pair every 60 seconds:
  DAIO45I WAITING FOR ACCESS TO OMCS DATABASE FILE
  DAIO45I TPOMCS.DATABASE.QPFCBJCL.FILE=.JOBDETLMASTER

TSO user in LTXF lockup screen display waiting for user to type their
password and press ENTER. Other address spaces are waiting to open a
database file held open by the first TSO user and are issuing messages:

  DAIO45I WAITING FOR ACCESS TO OMCS DATABASE FILE
  DAIO45I TPOMCS.DATABASE.QPFCBJCL.FILE=.JOBDETLMASTER

_PROBLEM SUMMARY:
USERS AFFECTED: TSO users of OMCS application functions

When an OMCS application function is trying to open a database file for
INPUT then the access method issues a SHARED ENQ for Q=ASEDAINP with a
resource name built from the database dsname and the database fileid.
If the ENQ is not satisfied within 60 seconds the access method will
issue WTO for a pair of DAIO45I messages identifying the resource which
it's waiting for.

In a TSO address space with PROFILE WTPMSG in effect each DAIO45I
message also appears as linemode output at the TSO terminal.  The first
DAIO45I message will cause the display to switch from fullscreen to
linemode.  If sufficient DAIO45I messages are written to fill the screen
(ie the file is unavailable for at least 10 minutes) then the "***" user
action prompt is written to the screen and the pending linemode TPUT
SVRB remains sitting on the end of the RB chain waiting for user action.

If the user is away from the terminal then it's possible for the
outstanding ENQ (represented by an SVRB higher up the active RB chain)
to acquire the resource, but be unable to complete because the TPUT SVRB
is below it on the RB chain.  The TPUT cannot complete until user action
occurs.  Thus this TSO user now has, and will be seen as holding, the
file resource SHARED.   While this does not prevent other users
concurrently acquiring the resource SHARED, if a user/job needs to open
the database file for UPDATE then this will result in an EXCLUSIVE ENQ
for the file resource.  This ENQ will back up behind the absent TSO
user's holding of the resource SHARED and will also prevent subsequent
users/jobs from acquiring the resource SHR thus creating a lockup which
can only be resolved by some user or operator action.

_PROBLEM CONCLUSION
RECOMMENDATION: Apply PTF ASP0911.

ASEDAMFM will be modified to issue the DAIO45I message pair once only
after the ENQ wait has persisted for 60 seconds.  No further messages
will be issued until the resource has been acquired, at which point a
subsequent DAIO45I message will be issued to report the successful
acquisition of the database file resource.

  DAIO45I TPOMCS.DATABASE.QPFCBJCL.FILE=.JOBDETLMASTER         ACQUIRED

By limiting the maximum number of DAIO45I messages that can be issued
to three we will avoid the overflowing linemode screen situation which
inevitably requires user action to clear.

Eventually, the TSO user's OMCS application function will wish to write
a fullscreen display to the screen, and this will cause "***" user
action prompt to appear.  However, the OMCS application will have closed
the relevant database file before the display is redriven thus
preventing a lockup.

NEED FURTHER HELP?  CALL ASE FOR ASSISTANCE.

       */
++VER(Z038) FMID(ASEB200) PRE(ASPnnnn).