Several times a week we receive alerts from DB2 Health Center concerning utilization of heap memory consumed by Health Monitor. Here is the message from logs:
ADM10500E Health indicator “Monitor Heap Utilization” (“db2.mon_heap_util”) breached the “upper” alarm threshold of “95 %” with value “200 %” on “instance” “DB2”. Calculation: “((db2.mon_heap_cur_size/db2.mon_heap_max_size)*100);” = “((655360 / 327680) * 100)” = “200 %”. History (Timestamp, Value, Formula): “()”
Even though MON_HEAP_SZ parameter of our DB2 instance is configured to be managed automatically alert still shows up. As it turned out it’s a minor DB2 bug. Which is described here. Short explanation of this bug follows:
Health Monitor is sending Alert to db2 user while Monitor Heap is set to Automatic.
So if in configuration parameters you see “AUTOMATIC” in Value column for MON_HEAP_SZ then you can safely ignore this alert. However, it’s not a good idea to have unresolved issues in Health Center. Besides, it’s rather annoying since it shows up quite regularly and bring our attention to it. The solution for this problem is to switch off monitoring of monitor these parameters by:
db2 update alert cfg for database manager using db2.mon_heap_util set THRESHOLDSCHECKED NO
db2 update alert cfg for databases using db.db_heap_util set THRESHOLDSCHECKED NO
What’s peculiar about this error is that according to IBM it was fixed in 9.5 and we work on 9.7 (regression bug?). On top of that, there is another bug JR31509 described here which is connected with the previous one. Short explanation:
The health indicator calculates the alarm threshold using db2.mon_heap_max_size, but this max size may not be increased even though the MON_HEAP_SZ is configured as AUTOMATIC.
That basically means that AUTOMATIC may not work properly and we might have memory issues in future. But I’ll keep my fingers crossed.
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