II13860: CF LOOP HIGH CF CPU UTILIZATION DB2 PERFORMANCE CASTOUT DSNB319A DSNB1CNE IXC585E Structure full

APAR status

• INTRAN

Error description

• Customers may experience High CPU utilization by Coupling
  facilities that contain DB2 Group Buffer Pool sturtures or may
  see struture full conditions on the GBP structures reported by
  either XCF or DB2 via DSNB319A or IXC585E messages.
  -
  A Coupling Facility Control Code (CFCC) Licensed Internal Code
  (LIC) problem exists that may cause CF CPU utilization to spike
  during periods of high group buffer pool (GBP) write/castout
  activity (e.g. DB2 RE-ORG jobs may drive this type of activity).
  The resulting CF activity may exclude or slow work directed to
  other structures in the affected CF which may result in an
  overall performance impact on the SYSPLEX.
  This problem is addressed on 206X machines with fix in CFCC
  Product Release 13 Service Level 4.05. The MCL is MCL022,
  Driver D3GF, and EC stream J11207.  For 208X machines the fix
  was introduced with D55K. Customers with questions questions
  about this maintence or who feel that they may have encountered
  this problem are encouraged to contact their IBM Customer
  Engineer (CE).
  -
  The following additional symptoms in the appropriate
  RMF reports will further confirm that this is the problem:
  -
     - CF utilization goes up while the request rate drops.
     - The GBP structures are relatively large.  e.g. hundreds of
       Megabytes
     - The write rate and castout rate on one or more GBP
       structures increase dramatically (as the CPU increases)
     - Average service times on most structures increase as
       utilization increases.
  

Local fix

• To reduce the likelihood of a reoccurrence of this problem the
  following tuning adjustments can be made for DB2:
     1) Put large NPI indexes in their own group buffer pool
        structure so they do not interact with smaller data sets.
     2) Change castout values to cast out changed data more
        frequently.  Some  customers have used values of GBPCHKPT
        as low as 2 minutes
  

Problem summary

Problem conclusion

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:

Fix information

Applicable component levels