This is just a plain file where all used tapes are listed, one line per used tape containing the tape VID and the nickname of the service that "owns" this VID. Lines starting with "#" and blank lines are ignored.

Normally the tape-related applications (such as backup or archiving systems) automatically require new empty tapes needed to store new data. The most efficient way to automatically provide a new tape to an application is to denote a list of free tapes ("tape pool"), along with a function that would "grab" a scratch tape out of the pool and mark it is as used by the service which requested a scratch tape.

In our case, the main configuration file denotes all managed tapes, and the "usedtapes" file mentions those that are in use. All the tapes that are not in use are considered as "empty tapes", and hence constitute the tape pool. Whenever a new tape is required by an application, server process consults both files, selects a first empty tape of the needed type, adds a corresponding tape line to the "usedtapes" file, and proceeds with a mount session.

The file is managed by the server process, and should not be changed by hand. The only case when the file may need to be edited is the deployment stage, when the Tape Dispatcher is being configured on the top of some legacy environment. Then both the main configuration and "usedtapes" files should be carefully introduced and verified, in order to make sure that i) all the needed tape VIDs are mentioned, and ii) all the used tape VIDs are "pool-protected" by mentioning them in the "usedtapes" file.

Here is how the "usedtapes" file looks like:

#########################################################
# This file denotes all used files in the system.
# It is managed by the Tape Dispatcher server process.
# DO NOT EDIT THIS FILE !
#########################################################
#
# VID  SERVICE_NICKNAME
#
LTO022 AFSBKUP
LTO023 AFSBKUP
LTO024 AFSBKUP
LTO048 STAGE  
CAS098 TSM
CAS099 TSM    
LTO025 AFSBKUP
LTO049 STAGE  
LTO026 AFSBKUP
################### END #################################