Re: Multiple instances of Oracle?

From: Magnus Lonnroth <mloennro_at_se.oracle.com>
Date: Thu, 13 Jan 1994 23:04:57 GMT
Message-ID: <MLOENNRO.94Jan13230457_at_demo1.se.oracle.com>

>>>>> "Bill" == Bill Chidester <bill_at_c3177208.ssr.hp.com> writes:

  Bill> This is a relay of a question posted for a friend -- please   Bill> excuse any obtuseness; it's a result of my translation...

I think our idea of an Oracle (database) instance may differ. See below.

  Bill> Is it possible to run multiple instances of Oracle (6.0) on   Bill> the same machine?

Yes, you can have any number of different Oracle db instances on most operating systems. You can have multiple instances sharing the same code, and/or multiple instances using different versions/releases of Oracle. Your PATH determines what binaries you will run. Your ORACLE_SID determines which Oracle instance you will connect to. On proprietary systems like VAX/VMS similar methods are used.

  Bill> It's possible to open multiple databases   Bill> with one instance of Oracle,

No. An Oracle instance consists of an SGA (shared memory structure) and a couple of background processes. An Oracle instance can manage one and only one Oracle database. There is *no* exception to this rule.

  Bill> but sometimes it is desirable to
  Bill> have one copy of the Oracle environment (with attendant
  Bill> pointers and buffers, etc) running while opening another
  Bill> database with another environment to avoid memory
  Bill> bottlenecking on the primary operation.  

Yes, you can have multiple instances (each with their own SGA and background processes) share an Oracle database. This is called the "parallel server" option in Oracle v7. In v6 it was first called Oracle v6.2, and later merged with v6.0 in v6.0.36. It is supported on loosely coupled systems such as VAX-clusters and various unix clusters, and also massively parallel computers, such as the nCube. The basic architecture is the same though.

If your Oracle release is greater than or equal to v6.0.36 or v6.2, *and* your hardware setup is supported for a parallel configuration, *and* you have a license to do so, you can create one database with multiple database instances. You are correct in predicting the benefits: reducing several types of contention - for example supporting a much larger number of concurrent users. There *can* be draw-backs too.

  Bill> After sampling two
  Bill> people knowledgeable in Oracle, I have two answers.  Person A:
  Bill> "Nope, can't do it.  Impossible!" and Person B: "Yep, I've
  Bill> done it.  Person A is obviously having some trouble with
  Bill> things he ingested back in the early '70's".

  Bill> Should belief be based on experience or psychodelics?

Belief is based on ethics. Ethics are based on society. Society is based on gasoline.

  Bill> --------------------------- Bill Chidester

  Bill> bill_at_hpuorfl.ssr.hp.com (Beware of the autoreply!)

--

Magnus Lonnroth
Tech.Sales & Consultant
Oracle Sweden
Mail: mloennro_at_se.oracle.com

Received on Fri Jan 14 1994 - 00:04:57 CET