OW29325: IST259I INOP01 IMMEDIATELY AFTER IST093I PU ACTIVE DURING ESCON CTC ACTIVATION.

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• During ESCON CTC activation msgIST093I PU ACTIVE appeared but
  was immediately followed by msgIST259I INOP CODE=01. While the
  channel end and and device end for XID7 was handled, the
  attention process walked past before the send/receive count was
  cleared by XID7 process. The follwoing start subchannel sent the
  bad count and caused the INOP 01.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All using CTC / MPC / AHHC connections.      *
  ****************************************************************
  * PROBLEM DESCRIPTION: MSGIST259I occurs at CTC/MPC/AHHC       *
  *                      activation just after completing XID.   *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  Here is the scenario for this APAR...Two process where running
  at the same time.  Process 1 is the completion of an XID.
  Process 2 is an Attention interrupt.
  
  Process 1                          Process 2
  ---------                          ---------
  1) CE/DE is received for and XID.
  2) The NCBPUPAB (ISTTSCXI) starts
     processing the XID completion.
  
                                  3) An Attention is received.
                                  4) An ATTN VIT entry is cut with
                                     an XCNSSFSM state of x'09'.
  5) ISTTSCXI changes the XCNSSFSM
     state to x'0B', but has not
     reset XCNOCTL because of
     FREEBLK processing of the PIO.
                                  6) ISTTSCCA checks XCNSSFSM for
                                     X'0B' and builds a READ
                                     channel program.  While
                                     building the CP, XCNOTCL is
                                     copied to YCNOBUF.
  7) XCNOCLT (send/receive counts
     XCNOPGCT and XCNOHDSZ)
     is now cleared.
                                  8) Start I/O VIT entry is cut
                                     with XCNOCTL = 0.  This
                                     field is copied from the
                                     XCNCB and not from the
                                     actual buffer to be sent out.
                                  9) SSCH traced with bad send/
                                     receive counts in the buffer.
  
  After this, the other host will INOP because of the invalid
  send receive counts.
  

Problem conclusion

• This timing window has been narrowed by not doing the FREEBLK
  processing of the PIO before resetting the send/receive counts
  in the XCNCB.  The send/receive counts will be reset immediately
  after going to XCNSSRDY (x'0B') state.  This should prevent
  the attention routine from detecting the X'0B' state and getting
  the invalid send/receive counts.
  

Temporary fix

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

  OW24478

• APAR is sysrouted TO one or more of the following:

  UW41848

Modules/Macros

• ISTTSCXE ISTTSCXI ISTTSC8E
  

Fix information

• Fixed component name

  VTAM V4 MVS/ESA

• Fixed component ID

  569511701

Applicable component levels

• R401 PSY UW41848

     UP97/10/15 P F710

Fix is available

• Select the PTF appropriate for your component level. You will be required to sign in. Distribution on physical media is not available in all countries.