Unique Volume Serial and Statistical Volumes

The total number of unique volume serials reported in GFTASRT2 often exceeds the number of statistical volumes reported in GFTASRT3. In GFTASRT2 (see Figure 1), the number of UNIQUE VOLSERS is the count of all volumes used during the analysis period.

Figure 1 provides a good example. If you run GFTAVMA against one single-file, single-volume data set that was created five times on five different volumes, and if those volumes were never reused, the count of UNIQUE VOLSERS in GFTASRT2 would be five.

Figure 1. Count of unique volsers for GFTASRT2

On day one of the study, data set D.E.F resided on volume 1.
               ┌────────────────────────────┐ 
VOLUME 1       │           D.E.F            │ old version 
               └────────────────────────────┘ 

On day four, a newer version of data set D.E.F resided on volume 2. 
               ┌────────────────────────────┐ 
VOLUME 2       │           D.E.F            │ old version 
               └────────────────────────────┘ 

On day 12, another version of data set D.E.F resided on volume 3. 
               ┌────────────────────────────┐ 
VOLUME 3       │           D.E.F            │ old version 
               └────────────────────────────┘ 

On day 23, an even newer data set D.E.F resided on volume 4. 
               ┌────────────────────────────┐ 
VOLUME 4       │           D.E.F            │ old version 
               └────────────────────────────┘ 

On day 30, the latest version of data set D.E.F resides on volume 5. 
               ┌────────────────────────────┐ 
VOLUME 5       │           D.E.F            │ current version 
               └────────────────────────────┘ 

Five different versions of data set D.E.F resided on five different volumes 
during the time of the study. 

The GFTASRT2 report shows the total count of volumes on which all versions of a data set
resided on during the period of the study (the number of unique volsers). 

For data set D.E.F, UNIQUE VOLSERS = 5

However, the statistical volume count in GFTASRT3 (see Figure 1) would be one, which is the count of the statistical volumes needed to hold the latest version of the data set as shown in Figure 2.

Figure 2. Count of statistical volumes for GFTASRT3

 
At the time of the study, the current version
of data set D.E.F is the version residing on volume 5.
              ┌────────────────────────────┐
VOLUME 5      │          D.E.F             │     current version
              └────────────────────────────┘
 
Volume 5 contains the current version of data set D.E.F,
and GFTAVMA assumes that volumes 1 to 4 were returned to
scratch because they contained old versions of data set D.E.F.
 
GFTASRT3 shows the count of the volumes that the current version
of a data set resides on during the study (statistical volumes).
 
For data set D.E.F, STATISTICAL VOLUMES = 1