HP OpenVMS Systems

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What is MUTEX state

The Question is:

I have the following question:

when a system "hangs" you have to force a crash, o.k. no
problem, just corrupt the stack en continue .

Go into SDA and SHOW SUM gives me the process states of the
processes.

Several processes are in MUTEX.

Q: What does a MUTEX do and why is my system hanging

I am NOT an expirienced user of SDA, only a system manager .

equipment: microvax 3100-90 VMS 5.5-2


p.s. english is sometimes difficult for a dutchie like me,
so sorry if i have choosen the wrong spelling or words.



regards,

The Answer is:

MUTEX is a state that means the process is waiting to own a mutex, which is
a synchronization structure within VMS.  Within SDA look at the Event flag
wait mask in the SHOW PROCESS display.  This should contain the address of
the MUTEX the process is waiting for.  If that address is the same as the
JIB address the the process has run out of either BYTLM or TQELM quota.
You can see which by looking at the JIB$B_FLAGS offset in the JIB.  If it
is a 1 then the process has run out of BYTLM if it is a 2 then the process
has run out of TQELM.  If the Event flag wait mask doesn't point to the JIB
address then the process is waiting on some other MUTEX.  To see which one
use EVAL {Event flag wait mask}.  You may be able to figure out who owns
the MUTEX by looking at the Mutex count field for all processes.  I suggest
you get the book VAX/VMS Internals and Data Structures (ISBN 1-55558-059-9)
as a further source of information on mutexes within OpenVMS.