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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@xxxxxxxxxx> 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@xxxxxx
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