Oracle and Postgresql Play Nice Together on Same Computer?

On Thu, 20 Jan 2005 00:03:28 -0500, Troyston Campano
<troygeekdatabase@gmail.com> wrote:

Hello,

I am an Oracle DBA and I want do a Postgresql 'proof of concept' at the
large corporation where I work to test the benefits of using Postgresql in
our environment. I want to install Postgresql onto a "production" server
that currently runs Oracle. Are there any problems with running Postgresql
and Oracle on the same machine? I mean, I've heard that the way Sybase and
DB2 UDB are architected to handle memory hurts Sybase when DB2 UDB is
installed on the same machine as the Sybase Server (something about UDB
eating up all the memory and not giving it back to Sybase).

Are there any issues running Postgresql and Oracle on the same
machine…anything special to know about memory, disk layout, and things like
that? I just want to make sure the two engines play together on this same
server. I had a hard time finding information about this via google.

For testing purposes there shouldn't be any problems, at least in a
*NIX environment. PostgreSQL is very undemanding and compared to
Oracle is positively minuscule (at least as far as its "installation
footprint" goes). I've run PostgreSQL, MySQL, DB2 and Oracle on the
same development machine without any issues. Of course if another
application is in constant use on a production server PostgreSQL won't
perform as well as it could.

Ian Barwick

Troyston Campano <troygeekdatabase@gmail.com> wrote on 20.01.2005,
06:03:28:

I am an Oracle DBA and I want do a Postgresql 'proof of concept' at the
large corporation where I work to test the benefits of using Postgresql in
our environment. I want to install Postgresql onto a "production" server
that currently runs Oracle. Are there any problems with running Postgresql
and Oracle on the same machine? I mean, I've heard that the way Sybase and
DB2 UDB are architected to handle memory hurts Sybase when DB2 UDB is
installed on the same machine as the Sybase Server (something about UDB
eating up all the memory and not giving it back to Sybase).

Are there any issues running Postgresql and Oracle on the same
machine.anything special to know about memory, disk layout, and things like
that? I just want to make sure the two engines play together on this same
server. I had a hard time finding information about this via google.

There should be no issues running both on the same machine. Running both
together at the same time isn't a good way of doing a benchmark
though...

I would question your intent slightly. Should it be a relative
comparison? Or should it be an assessment of what PostgreSQL is capable
of and whether that fits a sufficient number of your needs to make it
worth adopting?

There are many ways to structure a decision as to whether PostgreSQL is
suitable for your (business?) needs. Which structure you choose is
likely to prejudice your decision, one way or the other. i.e. if
capital acquisition costs are the decising factor, then PostgreSQL
would always win.

Best Regards, Simon Riggs

On Thu, 20 Jan 2005 simon@2ndquadrant.com wrote:

Troyston Campano <troygeekdatabase@gmail.com> wrote on 20.01.2005,
06:03:28:

I am an Oracle DBA and I want do a Postgresql 'proof of concept' at the
large corporation where I work to test the benefits of using Postgresql in
our environment. I want to install Postgresql onto a "production" server
that currently runs Oracle. Are there any problems with running Postgresql
and Oracle on the same machine? I mean, I've heard that the way Sybase and
DB2 UDB are architected to handle memory hurts Sybase when DB2 UDB is
installed on the same machine as the Sybase Server (something about UDB
eating up all the memory and not giving it back to Sybase).

Are there any issues running Postgresql and Oracle on the same
machine.anything special to know about memory, disk layout, and things like
that? I just want to make sure the two engines play together on this same
server. I had a hard time finding information about this via google.

There should be no issues running both on the same machine. Running both
together at the same time isn't a good way of doing a benchmark
though...

I would question your intent slightly. Should it be a relative
comparison? Or should it be an assessment of what PostgreSQL is capable
of and whether that fits a sufficient number of your needs to make it
worth adopting?

There are many ways to structure a decision as to whether PostgreSQL is
suitable for your (business?) needs. Which structure you choose is
likely to prejudice your decision, one way or the other. i.e. if
capital acquisition costs are the decising factor, then PostgreSQL
would always win.

I may add that using the right tool for the right task should be
a priority. It's easy to underestimate the cost of continuosly
adapting your needs to the tool and not the opposite.

About Oracle I keep hearing success or horror stories. About PostgreSQL
mostly success stories, some unsuccess stories ("it's good but we switched
back to MS SQL" ), _very_ few horror stories. Last horror story was
about "data worth having but not backupping", a category existing only
in some manager's mind (and _deserving_ a horror story).

Note that I've never heard any unsuccess story about Oracle. I know
some people that would tell one, if only they actually tried PostgreSQL
out - but that's my opinion, not thiers (yet).

IMHO, migrating from Oracle to PostgreSQL usually doesn't expose
all PostgreSQL pros, and will expose some weaknesses or missing features.
Migrating from PostgreSQL to Oracle is what really makes PostgreSQL shine.
Too bad it happens so rarely. :-)

.TM.
--
____/ ____/ /
/ / / Marco Colombo
___/ ___ / / Technical Manager
/ / / ESI s.r.l.
_____/ _____/ _/ Colombo@ESI.it

I guess what I am concerned about *is* running on a production server more
than a test server. Basically, I'd be taking a couple applications that are
running on the Oracle database instance, building a Postgresql instance, and
migrating them to that postgresql database instance. I'm just wondering
whether it's a bad idea to run them on the same server machine in a
production environment. (So instead of having 10 applications running on
Oracle on ServerComputerA...build a new postgresql instance on
ServerComputerA that lives along with Oracle and migrating 3 of the
applications to Postgresql.

Thank you for your time!

~ Troyston Campano ~

-----Original Message-----
From: Ian Barwick [mailto:barwick@gmail.com]
Sent: Thursday, January 20, 2005 3:07 AM
To: Troyston Campano
Cc: pgsql-admin@postgresql.org; pgsql-general@postgresql.org
Subject: Re: [GENERAL] Oracle and Postgresql Play Nice Together on Same
Computer?

On Thu, 20 Jan 2005 00:03:28 -0500, Troyston Campano
<troygeekdatabase@gmail.com> wrote:

Hello,

I am an Oracle DBA and I want do a Postgresql 'proof of concept' at the
large corporation where I work to test the benefits of using Postgresql in
our environment. I want to install Postgresql onto a "production" server
that currently runs Oracle. Are there any problems with running Postgresql
and Oracle on the same machine? I mean, I've heard that the way Sybase and
DB2 UDB are architected to handle memory hurts Sybase when DB2 UDB is
installed on the same machine as the Sybase Server (something about UDB
eating up all the memory and not giving it back to Sybase).

Are there any issues running Postgresql and Oracle on the same
machine.anything special to know about memory, disk layout, and things

like

that? I just want to make sure the two engines play together on this same
server. I had a hard time finding information about this via google.

For testing purposes there shouldn't be any problems, at least in a
*NIX environment. PostgreSQL is very undemanding and compared to
Oracle is positively minuscule (at least as far as its "installation
footprint" goes). I've run PostgreSQL, MySQL, DB2 and Oracle on the
same development machine without any issues. Of course if another
application is in constant use on a production server PostgreSQL won't
perform as well as it could.

Ian Barwick

Basically, we want to take 3 of the 10 applications running on Oracle, move
them to Postgresql on the same computer/server and just make sure it runs
about the same (really speed, memory usage, and space are the big issues).
I'm not concerned with how hard the migration will be and things like that.
The database is very low in complexity so the migration should be cake.

Thank you!

-----Original Message-----
From: simon@2ndquadrant.com [mailto:simon@2ndquadrant.com]
Sent: Thursday, January 20, 2005 4:20 AM
To: Troyston Campano
Cc: pgsql-admin@postgresql.org; pgsql-general@postgresql.org
Subject: Re: [ADMIN] Oracle and Postgresql Play Nice Together on Same
Computer?

Troyston Campano <troygeekdatabase@gmail.com> wrote on 20.01.2005,
06:03:28:

I am an Oracle DBA and I want do a Postgresql 'proof of concept' at the
large corporation where I work to test the benefits of using Postgresql in
our environment. I want to install Postgresql onto a "production" server
that currently runs Oracle. Are there any problems with running Postgresql
and Oracle on the same machine? I mean, I've heard that the way Sybase and
DB2 UDB are architected to handle memory hurts Sybase when DB2 UDB is
installed on the same machine as the Sybase Server (something about UDB
eating up all the memory and not giving it back to Sybase).

Are there any issues running Postgresql and Oracle on the same
machine.anything special to know about memory, disk layout, and things

like

that? I just want to make sure the two engines play together on this same
server. I had a hard time finding information about this via google.

There should be no issues running both on the same machine. Running both
together at the same time isn't a good way of doing a benchmark
though...

I would question your intent slightly. Should it be a relative
comparison? Or should it be an assessment of what PostgreSQL is capable
of and whether that fits a sufficient number of your needs to make it
worth adopting?

There are many ways to structure a decision as to whether PostgreSQL is
suitable for your (business?) needs. Which structure you choose is
likely to prejudice your decision, one way or the other. i.e. if
capital acquisition costs are the decising factor, then PostgreSQL
would always win.

Best Regards, Simon Riggs

On Thu, Jan 20, 2005 at 08:03:42AM -0500, Troyston Campano wrote:

Basically, we want to take 3 of the 10 applications running on Oracle, move
them to Postgresql on the same computer/server and just make sure it runs
about the same (really speed, memory usage, and space are the big issues).
I'm not concerned with how hard the migration will be and things like that.

So you want Postgres to be a cheaper Oracle. Hmm. Maybe it will work,
but as Marco Colombo says, you are not going to see Postgres shining by
using that simplistic approach. If you want that, maybe you should look
closely to see where you can find the rusty corner that needs to be
polished.

The database is very low in complexity so the migration should be cake.

If you do things as simple as "select count(*) from table", then you
will have to be careful to be really fair in your comparison; you could
misleadingly find that Postgres is much slower on that query.

--
Alvaro Herrera (<alvherre[@]dcc.uchile.cl>)
Tulio: oh, para qu� servir� este boton, Juan Carlos?
Policarpo: No, al�jense, no toquen la consola!
Juan Carlos: Lo apretar� una y otra vez.

[ Cc: list cleaned a bit ]

On Thu, 20 Jan 2005, Alvaro Herrera wrote:

On Thu, Jan 20, 2005 at 08:03:42AM -0500, Troyston Campano wrote:

Basically, we want to take 3 of the 10 applications running on Oracle, move
them to Postgresql on the same computer/server and just make sure it runs
about the same (really speed, memory usage, and space are the big issues).
I'm not concerned with how hard the migration will be and things like that.

So you want Postgres to be a cheaper Oracle. Hmm. Maybe it will work,
but as Marco Colombo says, you are not going to see Postgres shining by
using that simplistic approach. If you want that, maybe you should look
closely to see where you can find the rusty corner that needs to be
polished.

The database is very low in complexity so the migration should be cake.

If you do things as simple as "select count(*) from table", then you
will have to be careful to be really fair in your comparison; you could
misleadingly find that Postgres is much slower on that query.

Yeah, that's precisely what I meant. The Oracle to PostgreSQL migration
is well worth considering a (partial) redesign.

Sometimes I happen to show some SQL queries I make (on PostgreSQL)
to an Oracle guy. Usually it goes like this:

1) hmm (ponders at the query)
2) ah!!! (realizes what the query does)
3) I didn't know you could do this! (excitement)
4) hmm (ponders again if that may work on Oracle as well)
5) no I can't do that in Oracle that way. I remember I did something
like that in the past with other 3 SQL developers. We had to write
a 300 lines long stored procedure, we got the locking right at the
third reimplementation only (we don't know if we do need the locking,
we asked our senior DBA but he was unsure as well, so we put it in,
we don't think it hurts anyway).

Ok, point 5) has been exaggerated to joke level, but you get the idea.

.TM.
--
____/ ____/ /
/ / / Marco Colombo
___/ ___ / / Technical Manager
/ / / ESI s.r.l.
_____/ _____/ _/ Colombo@ESI.it

I'm not really too concerned about the migration aspect at all. If
need be, we might even throw in some new applications into the
postgresql database. What we're really concerned about is any issues
that may come from running postgresql and oracle on the same box. Do
they play nice together...or does one hog memory in a way that
prevents the other engine from operating correctly? I'm worried more
about things like that.

thank you again for your time!

~ Troyston ~

On Thu, 20 Jan 2005 15:22:33 +0100 (CET), Marco Colombo
<pgsql@esiway.net> wrote:

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Does anyone know if there could be a shared memory issue here?

If there is, then one of the two (postgres or oracle) would simply
refuse to start (it would quit with an error, I'd assume). If this
happens, you would need to either decrease the number of shared memory
resources one database or the other is asking for, or increase the
number of shared memory resources made available by the kernel (the
exact process depends on your operating system; I forget if you named
the one you are using or not).

Otherwise, there shouldn't be a problem, as long as your server
hardware has the resources to handle both at the same time (disk space,
memory/CPU power, etc.)

On Jan 20, 2005, at 10:50 AM, troyston campano wrote:

I'm not really too concerned about the migration aspect at all. If
need be, we might even throw in some new applications into the
postgresql database. What we're really concerned about is any issues
that may come from running postgresql and oracle on the same box. Do
they play nice together...or does one hog memory in a way that
prevents the other engine from operating correctly? I'm worried more
about things like that.

thank you again for your time!

~ Troyston ~

On Thu, 20 Jan 2005 15:22:33 +0100 (CET), Marco Colombo
<pgsql@esiway.net> wrote:

[ Cc: list cleaned a bit ]

On Thu, 20 Jan 2005, Alvaro Herrera wrote:

On Thu, Jan 20, 2005 at 08:03:42AM -0500, Troyston Campano wrote:

Basically, we want to take 3 of the 10 applications running on
Oracle, move
them to Postgresql on the same computer/server and just make sure
it runs
about the same (really speed, memory usage, and space are the big
issues).
I'm not concerned with how hard the migration will be and things
like that.

So you want Postgres to be a cheaper Oracle. Hmm. Maybe it will
work,
but as Marco Colombo says, you are not going to see Postgres shining
by
using that simplistic approach. If you want that, maybe you should
look
closely to see where you can find the rusty corner that needs to be
polished.

The database is very low in complexity so the migration should be
cake.

If you do things as simple as "select count(*) from table", then you
will have to be careful to be really fair in your comparison; you
could
misleadingly find that Postgres is much slower on that query.

Yeah, that's precisely what I meant. The Oracle to PostgreSQL
migration
is well worth considering a (partial) redesign.

Sometimes I happen to show some SQL queries I make (on PostgreSQL)
to an Oracle guy. Usually it goes like this:

1) hmm (ponders at the query)
2) ah!!! (realizes what the query does)
3) I didn't know you could do this! (excitement)
4) hmm (ponders again if that may work on Oracle as well)
5) no I can't do that in Oracle that way. I remember I did something
like that in the past with other 3 SQL developers. We had to write
a 300 lines long stored procedure, we got the locking right at the
third reimplementation only (we don't know if we do need the
locking,
we asked our senior DBA but he was unsure as well, so we put it in,
we don't think it hurts anyway).

Ok, point 5) has been exaggerated to joke level, but you get the idea.

.TM.
--
____/ ____/ /
/ / / Marco Colombo
___/ ___ / / Technical Manager
/ / / ESI s.r.l.
_____/ _____/ _/ Colombo@ESI.it

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It depends how you have your Oracle instance configured. If you have
it set up so that the total SGA and UGA ammount consume around 80%-90%
of total available memory, then this is obviously only going to leave
postgress with 20% or less of the total available memory. Postgres is
also designed to take advantage of the file caching behaviour of the
OS. The OS however is probably going to prioritize Oracle running
memory over cached file pages, and therefore I would think that
running the two together is a less than optimal configuration. If you
are going to do it, I would make sure that you at least reduce the SGA
for Oracle down below 40% of the box's total RAM so you give
postgresql enough space to work in. Even doing this, there is a
chance that the OS will try to cache the Oracle Tablespace files if
they are small enough, duplicating the buffering effort that Oracle is
doing, and also reducing the amount of memory for Postgresql file
cache.

All in all, I would personaly be very wary of running both together if
you are planning on doing any benchmarking.

Alex Turner
NetEconomist

On Thu, 20 Jan 2005 10:20:02 +0100, simon@2ndquadrant.com
<simon@2ndquadrant.com> wrote:

On Wed, 2005-01-19 at 23:03, Troyston Campano wrote:

Hello,

I am an Oracle DBA and I want do a Postgresql ‘proof of concept’ at
the large corporation where I work to test the benefits of using
Postgresql in our environment. I want to install Postgresql onto a
“production” server that currently runs Oracle. Are there any problems
with running Postgresql and Oracle on the same machine? I mean, I’ve
heard that the way Sybase and DB2 UDB are architected to handle memory
hurts Sybase when DB2 UDB is installed on the same machine as the
Sybase Server (something about UDB eating up all the memory and not
giving it back to Sybase).

Are there any issues running Postgresql and Oracle on the same
machine…anything special to know about memory, disk layout, and things
like that? I just want to make sure the two engines play together on
this same server. I had a hard time finding information about this via
google.

The only issue you're likely to face is the one you've already
mentioned, that Oracle may be configured to use most of the memory on
the machine, and PostgreSQL, in general, relies on the OS to do the
caching for it. Since there might not be much free / cache memory on the
machine, PostgreSQL may run a bit slower than it would were it the only
thing on the machine.

However, you can always do a benchmark with Oracle running, then shut
down oracle for a few minutes and see if PostgreSQL runs any faster with
the extra memory being used by the OS to cache the dataset.

Are there any issues running Postgresql and Oracle on the same
machine.anything special to know about memory, disk layout, and things
like
that? I just want to make sure the two engines play together on this
same
server. I had a hard time finding information about this via google.

We currently run Oracle and Pg 7.4.6 in production on a Solaris 8 box
with no problems. The only concern we have had is with the freakiness
of the /etc/system message queue, semaphore and shared memory settings.
Several apps seem to consume these finite resources and most of them
quietly act strangely and lose data when these resources are depleted.
Very few applications document what resources they *really* need.

There is probably a slick way to monitor these settings and determine
the right numbers for these, but we have not found it. Right now the
technique is "set, boot and pray."

BTW, concern with these resources is the sole reason we are hesitant to
install a slave server running 8.0 so that we can migrate. We will be
on 7.4 for some time.

Other than that, we have had no problems with running both Oracle and Pg
together on a production machine.

On Thu, 2005-01-20 at 06:58, Troyston Campano wrote:

I guess what I am concerned about *is* running on a production server more
than a test server. Basically, I'd be taking a couple applications that are
running on the Oracle database instance, building a Postgresql instance, and
migrating them to that postgresql database instance. I'm just wondering
whether it's a bad idea to run them on the same server machine in a
production environment. (So instead of having 10 applications running on
Oracle on ServerComputerA...build a new postgresql instance on
ServerComputerA that lives along with Oracle and migrating 3 of the
applications to Postgresql.

Have you got a spare machine you can do the testing on at first? That
will allow you to throw big nasty queries at the server and tune it
first, before putting postgresql on the production box.

I'd recommend reading the tuning document from varlena:

http://www.varlena.com/varlena/GeneralBits/Tidbits/perf.html

And experimenting with various settings on a test box first. My first
PostgreSQL server way back when was running 6.5.2 or so on my P-II-300
workstation with 128 Megs of ram sitting under my desk, and it ran quite
well, well enough we used it as our development / staging server for
almost a year.