Tape Devices in DLm Show SUBSYSTEM equal 00 in 'q config' Despite SUBSYSTEM equal 1 in CU Config
Summary: In DLm Version 5.1.2, the requirement to specify SUBSYSTEM= in the device TAB has been removed. Up to 32 control units, each with 16 tape devices, can now be defined without including a SUBSYSTEM value. ...
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Symptoms
In DLm GEN5 Version 5.1.2, control units defined with SUBSYSTEM=1 may appear as SUBSYSTEM=00 when viewed using the q config command.
This occurs in environments where up to 32 control units (CUs), each supporting 16 tape device numbers, are configured on a single VTE. The CU number in the Token NED allows each control unit to be uniquely identified and displayed using the d m=cu(<CU number>) command.
Cause
As of DLm Version 5.1.2, support for multiple subsystems using the SUBSYSTEM= parameter has been removed. The parameter no longer has functional meaning and is internally hard coded to SUBSYSTEM=00. As a result, all devices display as SUBSYSTEM=00 in q config, regardless of any SUBSYSTEM value specified in the configuration.
Resolution
The SUBSYSTEM parameter is no longer required when defining control units in the Device TAB of the DLm Version 5.1.2 Web Console. As the Web Console evolves, this parameter will be removed entirely in future code releases.
Up to 32 control units, each containing 16 tape device numbers (totaling 512 tape devices), can be defined without specifying SUBSYSTEM. After installation, the q config command shows all tape devices as SUBSYSTEM=00, even if a different value was defined in the configuration.
Affected Products
Disk Library for mainframe, Disk Library for mainframe DLm8500Article Properties
Article Number: 000078600
Article Type: Solution
Last Modified: 21 Aug 2025
Version: 3
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