Environment variables are used to communicate information about a backup or restore operation between an NDMP-enabled backup application and a storage system.
For example, if a user specifies that a backup application should back up /vol/vol0/etc, the backup application sets the FILESYSTEM environment variable to /vol/vol0/etc. Similarly, if a user specifies that a backup should be a level 1 backup, the backup application sets the LEVEL environment variable to 1 (one).
A backup administrator rarely specifies environment variables; however, you might want to change the value of an environment variable from that set by the backup application to characterize or work around a functional or performance problem. For example, an administrator might want to temporarily disable file history generation to determine if the backup application's processing of file history information is contributing to performance issues or functional problems.
Many backup applications provide a means to override or modify environment variables or to specify additional environment variables. For information, see your backup application documentation.