OA50868: XCF I/O DELAYED AFTER LOSING ALL PATHS

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• After losing access to all paths to a non-HyperSwap managed
  device, certain I/O could be delayed behind IOS recovery
  attempts.  This APAR will improve the design.
  
  KNOWN IMPACT:
  XCF I/O to the Sysplex CDS could be delayed if all paths are
  lost to that device during a HyperSwap
  
  
  VERIFICATION STEPS:
  Verify that a "no paths available" condition was raised
   IOS002A 1234,NO PATHS AVAILABLE
  
  From the IOS component trace seen with IP CTRACE COMP(SYSIOS)
  SUMM, the device will be validated several times from Dynamic
  Pathing Validation (DPSV).
    DPS   000F0001  14:36:17.586231  Dynamic Pathing SNID Data
     Device: 01234
       ...
  
  There will be multiple I/O timeouts for queued I/O requests,
  AFTER the time of the IOS002A message.
    IOS079I 1234,51,XCFAS, I/O TIMEOUT INTERVAL HAS BEEN EXCEEDED
    FOR A QUEUED REQUEST. THE QUEUED REQUEST HAS BEEN TERMINATED.
  
  From IOS component trace, verify the I/O requests had flag
  IOSCC3WE set in the IOSB (x'20' bit at IOSB+2).
  
  
  ADDITIONAL SYMPTOMS:
  UCBNOPTH HYPERSWAP HIPERSWAP CDS IXCSETUS ENF63
  

Local fix

• BYPASS/CIRCUMVENTION:
  None, all I/O should complete after some period of time
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: Users at HBB7790 and above.                  *
  ****************************************************************
  * PROBLEM DESCRIPTION: After all paths are lost on a DASD      *
  *                      device that contains a Couple Data Set  *
  *                      (CDS), XCF I/Os are delayed due to long *
  *                      wait time in IOS channel path recovery. *
  *                      When the path loss occurs during a      *
  *                      HyperSwap, the delays of XCF I/Os may   *
  *                      cause the HyperSwap to fail.            *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  I/Os are in long delays after a DASD device loses all paths due
  to recovery time using the device's Device Dependent Timeout
  (DDTO) which is defaulted to 45 seconds.
  
  If the device losing the paths happens to contain a Couple Data
  set (CDS), XCF I/Os will be delayed waiting for IOS recovery
  processing to complete instead of being posted back with a DCC3
  code which will enable XCF to switch to its alternate CDS.
  
  When the path loss occurs on a device containing a CDS during
  a HyperSwap, the delayed I/Os will also affect HyperSwap and
  may even cause the HyperSwap to fail.
  

Problem conclusion

• To fully address the reported issue, this APAR along with XCF
  APAR OA50939 provide a way for IOS to recognize if a DASD
  device contains a Couple Data Set. When a path loss event
  occurs on such device, IOS channel path recovery will return
  immediately so that XCF can switch to the alternate Couple
  Data Set, allowing the I/Os to complete.
  Update has also been made to prevent binding aliases to a base
  device that has no active path.
   KEYWORDS: HYPERSWP/K
  

Temporary fix

Comments

APAR Information

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

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

  OA50939 UA83990 UA83991

Modules/Macros

• IECVGENA IOSGEN   IOSRSNDV IOSVSSCH
  

Fix information

• Fixed component name

  IOS

• Fixed component ID

  5752SC1C3

Applicable component levels

• R7A0 PSY UA83990

     UP17/02/22 P F702

• R790 PSY UA83991

     UP17/02/22 P F702

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.