Re: Server hang after SELECT command

1999-05-18 04:39:02
Subject: Re: Server hang after SELECT command
From: Alexander Verkooijen <alexander AT SARA DOT NL>
Date: Tue, 18 May 1999 10:39:02 +0200
On 17-May-99 Thomas Denier wrote:

> I am now decidedly nervous about running complex select commands. Does anyone
> have any information on the dividing line between select commands that are
> safe and select commands that cause hang conditions?

We had an almost similar problem today.

I entered a pretty complex select command before I left the office
yesterday. When I came back this morning the command was still running.
Other select commands that were started during the night by
automated scripts were also still running (hanging).
Normally it takes only a few seconds for these commands to complete.

It was still possible to open a server session and I entered a very
simple command: select drive_name from drives
To my suprise this command generated a few lines of output and
terminated normally.

Then I tried a slightly more complex command:
select node_name from filespaces
I waited for a long time but this command generated
no output whatsoever.

At that time there were several admin-sessions running on the
sever as a result of all the hanging select commands that I had
killed. I tried to cancel one of those sessions, but that appeared
to be impossible.

I halted the server and restarted it and everything worked fine again.

I must admit that I find this situation a bit scary. We rely on select
commands to monitor the status of the server and the backups and this
is the first time we have seen something like this happen.


Alexander ( on AIX 4.2.1)

Alexander Verkooijen     SARA
Alexander Verkooijen     SARA
Systems Programmer       Academic Computing
alexander AT sara DOT nl        Services Amsterdam
<Prev in Thread] Current Thread [Next in Thread>