IBM Support

PH27734: ZWAS POOR FILESYSTEM PERFORMANCE DUE TO CKACCESS / FSACCESS CML LOCK CONTENTION

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APAR status

  • Closed as program error.

Error description

  • Under heavy load it is possible to see poor filesystem
    performance in zWAS servants due to CML lock contention on
    ckaccess paths for RACF class FSACCESS.
    Dump systrace analysis
    shows 2 CML lock obtains for the ZFS address space for each
    ckaccess request.
    
    This APAR was taken to call
    RACROUT
    REQUEST=LIST,...CLASS=FSACCESS
    during zWAS servant
    initialisation.
    
    This will reduce the number of CML lock
    obtains from RACF code on this path.
    

Local fix

  • Disable FSACCESS checking in RACF.
    

Problem summary

  • ****************************************************************
    * USERS AFFECTED:  All users of IBM WebSphere Application      *
    *                  Server                                      *
    *                  V9.0                                        *
    ****************************************************************
    * PROBLEM DESCRIPTION: WebSphere Application Server for z/OS   *
    *                      poor performance with FSACCESS profile  *
    ****************************************************************
    * RECOMMENDATION:                                              *
    ****************************************************************
    The FSACCESS profile is used to control access to the file
    system.  The CML lock is used to make the access checks even if
    the profile is RACLIST'd.  This caused significant delays when
    under load.
    

Problem conclusion

  • Code was modified in the Servant address space to issue a
    RACROUT REQUEST=LIST for class FSACCESS during the Servant
    initialization if a new environment variable is set to "1".
    
    The RACROUT REQUEST=LIST issued within the Servant address
    space creates a local copy of the profile information within
    private storage of the Servant.  Access checks made on the
    FSACCESS class from the Servant will use this private storage
    without the need to obtain the CML lock.
    
    The new environment variable is
    server_region_racroute_list_fsaccess.  The default value is
    "0".
    
    The fix for this APAR is targeted for inclusion in fix pack
    9.0.5.7. For more information, see 'Recommended Updates for
    WebSphere Application Server':
    https://www.ibm.com/support/pages/node/715553
    

Temporary fix

Comments

APAR Information

  • APAR number

    PH27734

  • Reported component name

    WEBSPHERE FOR Z

  • Reported component ID

    5655I3500

  • Reported release

    900

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2020-07-22

  • Closed date

    2020-12-16

  • Last modified date

    2020-12-16

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

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

Fix information

  • Fixed component name

    WEBSPHERE FOR Z

  • Fixed component ID

    5655I3500

Applicable component levels

[{"Line of Business":{"code":"LOB36","label":"IBM Automation"},"Business Unit":{"code":"BU053","label":"Cloud & Data Platform"},"Product":{"code":"SS7K4U","label":"WebSphere Application Server for z\/OS"},"Platform":[{"code":"PF025","label":"Platform Independent"}],"Version":"900"}]

Document Information

Modified date:
12 January 2021