A manual tape library (MTL) is an installation-defined set of tape drives and a customer-defined set of tape volumes with mount capability on those tape drives. The volumes can be physically stored in shelf storage located near the MTL, but since these volumes are specifically defined as residing in the MTL, they are known as library-resident volumes. When the volumes are logically ejected from the MTL, they become shelf-resident volumes.

In an MTL environment, the operator or tape librarian responds to commands at the MVS console, manually loading and unloading the tape cartridges. Before a tape cartridge can be used, the tape cartridge must first be logically entered into an MTL. Cartridges can be entered into an MTL through invocation of the CBRXLCS manual cartridge entry (MCE), general use programming interface, or through invocation of the LIBRARY ENTER command (see Entering a tape volume into an MTL for more information).