Re: postmaster.pid

Hi,

On Friday 03 January 2003 18:38, you wrote:
> > > i think that somewhere in the docs the administators
> > > should be advised to delete postmaster.pid automatically at boot
> > > time ( for example at the same time when the files in /tmp are
> > > deleted ).
> > > This way, in case of an unexpected shutdown, postgresql would be
> > > able to restart without any manual intervention.
> >
> > Well, this is a *BAD IDEA*. Suppose, for example, your data is corrupt in
> > some special way, an due to your removal of the pid file, postmaster
> > tries to recover the database automatically and probably destroys all or
> > data part of the data. You would like to have been able to do a
> > filseystem level backup first...
>
> Ooopss...  it seems like i am too optimistic about such situations.
>
> Just wondering: if the database is so heavily damaged that the
> postmaster would not be able to recover,  are there any chances to
> restore anything from a filesystem backup, manually ?
>

With a lot of work, sometimes... it all depends of how much the data is worth
to (read: when did you do you last backup? ;-)

> .........
>
> Background:
>   - our team is working on a project for a small company.
>   - there will be one server and 3-4 clients
>   - It is the first time we use PostgreSQL.
>   - Little space.
>   - Many people around.
>   - No UPS (yet).
>   - unpredictable,untrained,desperate,'crazy' users
>
> Possible problems:
>   - the users will need time to learn how to use the program
>     ( until then they could do many mistakes, such as turning off the
>       server before leaving the office - without issueing the proper
>       shutdown command, but simply pushing the power switch. )
>   - someone might stumble over the cable and unplug the server by mistake.
>

Why should someone switch off a server at all? Except for maintenance or
repair?

> Questions:
>   How resistent is PostgreSQL to such shocks?
>
It never failed me after a crash. But I don't push it... (I can remember only
3 crashes at all, and these were NOT PostgreSQL's fault!)

>   Are there alternative solutions to handling unexpected shutdowns
>   automatically?   (except deleting postmaster.pid at boot time)
>

The best idea for your situation seems to be the advice: make automated
backups as often as possible, to avoid too much data loss. Then you could go
the route of 'delete pid file automatically'.

If a really bad thing happens, you can always restore from tha last backup.

>
>
> Best wishes,
>
> Adrian Maier
> (am@fx.ro)
>
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HTH,
    Joerg
--
Leading SW developer  - S.E.A GmbH
Mail: joerg.hessdoerfer@sea-gmbh.com
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