MICS product change, DB26945, improves the precision of several MICS IDAA CPU Time Data Elements.
Specifically,
DSUXAELA - IDAA Elapsed Time
DSUXAWAT - IDAA Wait Time
DSUXSCPU - IDAA Services CPU Time
DSUXSELA - IDAA Services Elapsed Time
DSUXACPU - IDAA CPU Time
DSUXDPWT - IDAA Delay Protocol Wait Time
Prior to DB26945, the initial problem was believed to be where the IDAA data elements were wrong by a factor of 4096.
However, after further investigation, this was determined to not be the case.
When comparing MICS values to IBM OMEGAMON reports, a difference was noticed where MICS values differ from IBM values, usually at the 4th decimal point.
After researching how MICS is inputting or modifying the raw fields (inputting with MAMSEC, then multiplying by 4096), it became obvious that MAMSEC divides a binary field by 4,096,000,000.
Multiplying by 4096 means the net result is that the original binary field is divided by 1,000,000.
A simpler approach would be to read the original raw field using PIB8.6 INFORMAT.
When using this method (inputting with PIB8.6), it was determined that the numbers more closely match IBM’s.
Ultimately, performing a single operation (dividing by 1,000,000) helps avoid intermediary rounding and truncation issues.
Here are some examples of our "before" and "after" results:
DSUXAWAT OLDX.DB2DSU01=0:00:00.002816 NEWX.DB2DSU01=0:00:00.002995
DSUXAWAT OLDX.DB2DSU01=0:00:00.003072 NEWX.DB2DSU01=0:00:00.003217
DSUXAWAT OLDX.DB2DSU01=0:00:00.003328 NEWX.DB2DSU01=0:00:00.003366
DSUXAWAT OLDX.DB2DSU01=0:00:00.003072 NEWX.DB2DSU01=0:00:00.003152
DSUXAELA OLDX.DB2DSU01=0:00:00.021760 NEWX.DB2DSU01=0:00:00.022003
DSUXAWAT OLDX.DB2DSU01=0:00:00.005888 NEWX.DB2DSU01=0:00:00.006043
DSUXAELA OLDX.DB2DSU01=0:00:00.018176 NEWX.DB2DSU01=0:00:00.018285
DSUXAWAT OLDX.DB2DSU01=0:00:00.005120 NEWX.DB2DSU01=0:00:00.005374
DSUXACPU OLDX.DB2DSU01=0:00:00.058368 NEWX.DB2DSU01=0:00:00.058606
DSUXAELA OLDX.DB2DSU01=0:00:00.017408 NEWX.DB2DSU01=0:00:00.017569
In summary, the MICS database is not corrupted with incorrect values; instead, the method used to convert raw data values to MICS data elements introduces some precision issues.
This is similar to problems where the LENGTH assigned to numeric data elements is too small.
By using the PIB8.6 input method, MICS improves the precision, and in all cases, any old values are slightly understated, usually in the 4th decimal place.
After making this input method change, the MICS numbers more closely match IBM OMEGAMON report numbers.
MICS Analyzer Option for DB2 r14.4
MICS Analyzer Option for DB2 r14.3
DB26945 - IDAA CPU Time Data Elements Improved Precision