IBM manual Magstar 3494 Tape Library Operator Guide

Five drop-down lists and a set of check boxes are used to set up an inhibit reclaim entry. The drop-down lists contain the following:

vDay of week

Sunday through Saturday or Every day. If ªEvery dayº is selected, the ªStart timeº and ªDurationº entered will apply to every day of the week.

vStart Hour and Minute

The start hour and minute for the inhibit. A 24 hour clock is used where 00 in the hour ®eld means midnight.

vDuration Hours and Minutes

The number of hours and minutes that the inhibit reclaim should remain in effect. Up to 167 hours and 59 minutes can be speci®ed (7 days minus 1 minute). Specifying the maximum will essentially always inhibit reclaim.

vCheck boxes to indicate which VTS to apply the schedule to.

Add an entry to the inhibit reclaim schedule by selecting a day of week, a start time,

the duration, then select the Add button.

Delete an entry by highlighting it in the list box then selecting the Delete button.

The Free Storage Threshold is used to provide a warning when the VTS is running

low on free storage, the capacity of all the empty stacked volumes in the VTS. A

threshold is provided for each VTS installed in the library and is entered in GB. The

default value is 100 GB. The VTS Active Data window displays the Free Storage

Threshold as the Free Storage Alarm Level. If the free storage drops below the

threshold (alarm level), the Library Manager signals an intervention-required

condition to notify the operator to add more stacked volumes.

The number of stacked volumes required to store the Free Storage Threshold GB

speci®ed on the Set VTS Management Policies window is dependent on the

compression of data when writing from the Tape Volume Cache to the stacked

volume. The 3494-B18 VTS with enhanced ESCON host attachments provides

compression into the Tape Volume Cache; therefore, further compression when

writing to the stacked volume is unlikely, and the capacity of a stacked volume will

be approximately 10 GB of Tape Volume Cache data. The earlier VTS, 3494-B16,

relied on the compression capability of the Magstar 3590 drives to store

approximately 20 GB of Tape Volume Cache data, assuming a compression ratio of

2:1.

The Free Storage Threshold of 100 GB requires ®ve empty cartridges for the model

B16 VTS; however, with the model B18 VTS, a Free Storage Alarm is sent when

only 10 empty stacked volumes are available because the Tape Volume Cache data

has already been compressed when received into the Tape Volume Cache.

Assuming a compression ratio of 3:1 with the enhanced ESCON host attachments,

an alarm at the Free Storage Threshold of 100 GB, representing 10 empty stacked

volumes, allows storage of 300 GB of logical volume data.

To get an alarm when the number of empty stacked volumes drops below 50, you

would specify a Free Storage Threshold of 500 GB on a model B18 with enhanced

ESCON attachments, and of 1000 GB on other VTS models.

The Reclaim Threshold Percentage is used to identify when a stacked volume is to

be made available for reclamation. Each stacked volume has some amount of

active data and some amount of inactive (no longer needed) data. If the percentage

of active data is less than the percentage speci®ed in this panel, the stacked

168Magstar 3494 Tape Library Operator Guide