Mutex server

Robert Feehan wrote:
> 
> We are having an interesting problem that I would like comments on.
> One of our programmers accidentally typed the following command and ran
> it: "help table *". When she didn't get any output back after a couple
> of minutes she hit Control C. Immediately after this our server hung
> in a MUTEX state. This problem has occurred 3 times as I didn't
> immediately track it down until the programmer notified me that she
> had done this each time our system hung.
> 
> We use OpenIngres 1.1/04 (axp.vms 01) and patch 3931. Our system is an
> ALpha 2100. Anybody seen this kind of behaviour?
> 
Hi Robert,

It's almost certainly a VMS resource shortage which is causing the
problem. DBMS servers (6.4 and OpenIngres) go into MUTEX state
when they have runout of buffer_limit quota. This is a problem
we see every now and then here in technical support in the UK,
so I'm reasonably confident this will solve your problem.

Here's a sample formula we use to compute the MINIMUM value for
buffer_limit - always add a contingency amount just in case.

	buffer_limit = 64 + (( file_limit - 1) * 96)

It's pretty crude as there are many more factors than just the file 
limit, but it will give you an idea of how close you are sailing
to the edge.

Good Luck,

Tony
----------------------------------------------------------------------
Tony Smith
tsmith@ingres.com
----------------------------------------------------------------------


   I've seen something similar, but it didn't crash the server. Both OI 
1.1 and 1.2 for the HP have a bug which causes help and help table to 
lock during an on-line checkpoint until the checkpoint completes. ODBC 
connections also hang in a MUTEX state for the duration of the 
checkpoint. Miscellaneous other functions will also lock, but as long as 
you avoid the help functions you can still run queries on the data (but 
not the system catalogs) through the terminal monitor. Patches are 
available for this on the HP.

Good luck
Neil Hammar
hammar@acm.org   {permanent address, mail forwarding account}
hammar@swcp.com   {current address}
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