5. FILES › 5.2 VMC Information Area Files › 5.2.2 VM Device Accounting File (VMCDAC) › 5.2.2.3 VMCDAC Usage Considerations

5.2.2.3 VMCDAC Usage Considerations

Special considerations or techniques related to using the
VMCDAC File are provided below:

DATA DUPLICATION CONSIDERATIONS

The VMCDAC File is created from VM Account device records.
When a device record is created, there is no identification
of the real or virtual device being accounted for.  If a
virtual machine has two devices that have the same
characteristics (e.g., two five-cylinder, 3380 temporary
disks) that have been attached to the virtual machine for the
same amount of time, the account records produced for these
two devices will be exactly the same.

It is possible for data to appear to be duplicated, when in
fact it is not.  Therefore, no attempt to drop duplicate data
in this file is made.  This means that, unlike other files,
VMCDAC is exposed to duplicate data due to the same data read
more than once in the same daily update.  If the SORT of the
VMCCMU File shows duplicate observations dropped, the VMCDAC
File is very likely to contain duplicate data.  This will
impact accounting if your installation is using the VMCDAC
File for cost recovery.

VIRTUAL DEVICE DATA

The VMCDAC File contains one observation per virtual device
that is attached, dialed, or dedicated to a virtual machine.
If your installation creates account data on an interval
basis (with a mechanism that uses the CP ACNT CLOSE ALL
command) or has a means of changing the account number for a
virtual machine dynamically, the number of observations will
increase by the number of times the ACNT command is issued
and/or the virtual machine account number is changed while
the virtual machine is logged on.

CHARGEBACK CONSIDERATIONS

If your installation wants to use the CA MICS Accounting and
Chargeback Product to charge for device usage, certain issues
should be considered when using the VMCDAC File.

Some installations may not want to charge for dedicated DASD
or may want to apply rates for dedicated DASD that are
different from those applied to temporary disk.  To determine
whether an observation is for dedicated DASD, check the
elements DEVCLASS and DACATYPE by using the following type of
algorithm:

 IF DEVCLASS EQ :'DASD' THEN DO;         /* DASD ?      */
   IF DACATYPE EQ :'PERM' THEN DO;       /* DEDICATED ? */


Different charges by device type can be made as follows:

 DTYPE = SUBSTR(DEVTYPE,1,4);
 SELECT (DTYPE);
   WHEN ('3380') THEN ...
   WHEN ('3350') THEN ...
   WHEN ('3480') THEN ...
   WHEN ('3420') THEN ...
   OTHERWISE NOP;
 END;