Most MVS™ commands are executed by attaching a task in either the *MASTER* or CONSOLE address space. If too many such tasks are attached at one time (usually because a program has issued too many MGCRE macros in too short a time), command flooding occurs.

Attached commands that run in the *MASTER* or CONSOLE address space are divided into six “command classes”. In each class, only 50 commands can execute at one time. Any additional commands in that class must wait for execution. This prevents an out-of-storage condition. To manage the number of commands that are awaiting execution, the system operator can issue the CMDS command to display the status of commands, and remove selected commands that are awaiting execution. The IEECMDS macro provides similar function.