IBM Magstar 3494 manual VTS Active Data Pop-Up Window

VTS Active Data

The Active Data window (Figure 71) displays a graph showing the amount of active

data, amount of free storage, maximum active data, and a free storage alarm level

for the stacked volumes in a VTS. The data stored on stacked volumes is from the

Tape Volume Cache and may be compressed when the VTS has the EHPO feature;

therefore, the graphs do not represent actual host data bytes, but the compressed

volume sizes as stored in the Tape Volume Cache. A separate graph is available for

each VTS in the library. Data is displayed for the previous 29 days as of midnight

and for the current day on an hourly snapshot.

Figure 71. VTS Active Data Pop-Up Window

Active Data is the total size, as stored in the Tape Volume Cache, of all active

logical volumes that have been copied to stacked volumes. Virtual volumes that

exist in the Tape Volume Cache but have not been copied to tape are not included.

Invalidated (non-active) copies of logical volumes are also not included in the graph.

Maximum Active Data is the total capacity of all stacked volumes that have been

inserted in the VTS. For the model B16, the Maximum Active Data is a theoretical

value computed by assuming that stacked volumes are ®lled with a 2:1

compression ratio. The model B18 uses the actual compression ratio achieved for

all data copied from the Tape Volume Cache to full stacked volumes to calculate the

Maximum Active Data. Because data received from enhanced ESCON host

attachments has previously been compressed into the Tape Volume Cache,

compression to the stacked volume from the Tape Volume Cache will be

approximately 1 to 1 for the B18. Note that invalidated copies of logical volumes

reduce the amount of active data you can store on the stacked volumes.

Chapter 6. Advanced Operating Procedures 123