HB.js high CPU usage after upgrade of CICS V5.3 to V5.5
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HB.js high CPU usage after upgrade of CICS V5.3 to V5.5


Article ID: 270529


Updated On:




After upgrading from CICS/TS V5.3 to vV5.5 it was found that CICS region (with HB.js) consumes 2-4 times the CPU time than it did before.
Other CICS regions (without HB.js) have no increase in CPU usage.


Release: 6.7.8
z/OS: 2.3


Hostbridge Engineering reviewed the output, AUXTRACEs, dumps and could not find a significant difference in the execution between CICS TS 5.3 and 5.5.
The AUXTRACE did not give CPU time but does show the interval between trace entries, if anything CICS 5.5 appears to be faster than 5.3.
A significant difference in how CICS was allocating certain files was observed. The allocation pattern in question was repeated nearly a million times on CICS TS 5.5.
Region            HB.js Sessions    Dataset Reallocations

CICS TS 5.5           993154                     993010
CICS TS 5.3           338311                             31
The freeing and reallocation of these files occurs in IBM code and may be responsible for the increased GP CPU utilization. 

Engineering requested that a ticket be opned with IBM for their analysis of the collected data.
After doing so IBM suggested setting the feature com.ibm.cics.ds.freeussprocesses=false and retest the HB.js transaction again.
The CPU usage was then reduced to around 0.0020 seconds.

Additional Information

CICS Transaction Server for z/OS > 5.5 > Feature toggles