The library manager (Figure 1, item 1 ) is a licensed internal code application installed in the library controller that controls all operations in the tape library. The library manager communicates with the host through each control unit, and allows communication paths for operators and service personnel. The library manager is also used for service and test sessions and provides operator status information and control panels for the operator’s use. Transaction logs and an error log are also provided as problem determination aids. For more information concerning the library manager for the 3494 ATLDS, see IBM TotalStorage Enterprise Automated Tape Library (3494) Introduction and Planning Guide.