# Monitor debugger

Use this tool to recover from system failures or when the virtual debugger cannot access
 the system resources.

The monitor debugger allows:

- displaying and changing D3 virtual memory.

- displaying and changing real memory (UNIX virtual memory).

- forcing a flush of the D3 memory space back to disk.

- displaying and changing the status of the system semaphores to remove a dead lock situation.

- accessing a locked system.

- terminating processes and shut down.

- tracing modifications to a memory area.

- putting low level breakpoints in the virtual code.

CAUTION: When the monitor debugger is entered unexpectedly,
first type g, and then press ENTER to restart the
system. If the system does not restart, press BREAK to examine the
problem. There are cases when the debugger is entered incorrectly.
For example, when long, unbreakable, tape operations (for example,
a rewind) are running, pressing BREAK several times
on line 0 may enter the monitor debugger with a tight loop condition.
This means that the process was engaged in a long operation, preventing
it from servicing the BREAK key.

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Source: https://d3codex.com/unix/monitor-debugger/ - part of the D3Codex reference.