Re: HELP - Oracle is kicking my ass!!!!!

mike <mike_at_bgl.psycha.edu.penn> writes:

>I'm the new DBA of an Oracle database system running on a DEC Alpha
>machine running Digital Unix. I have been using svrmgrm to do dba-like
>things, but I'm confused on a few things. My former experience was on
>Informix systems, which seem to be different in some ways.

Welcome to the club. It doesn't get better - you just get used to it.

>First, I can view table spaces, and datafiles, and such, but I'm never
>prompted to select a database per se. Where is the database? I don't
>even know how many databases we have set up? It's a small lab here, and
>I think there's only one, but none of the tools have a selection called
>"SELECT DATABASE". If I did have two databases, how would they be
>specified?

In Oracle, you have the database and the instance. The instance is the memory part, and the database is the file part (to put it simply). When you started up svrmgrm, you put in your name and password and perhaps a database alias - that's the database you logged into. When you log into a database, you are exclusively connected to that database.

>How does one create a database not-by-hand. Is there some automatic
>method?

Mmm, you can use orainst (Oracle Installer) to create a starter database. But it is best (in my opinion) to do it by hand. This involves editing an init.ora file, setting your SID, starting an instance, and running the create database command (this is all documented in the admin guide, or the DBA Manual by Oracle Press). If you'd like a comprehensive walkthrough, e-mail me.

>I'm confused here because with Informix, the first thing you do is
>select a database to work with. I understand that in oracle, that you
>have table spaces, and then you have datafile (*.dbf files) within those
>table spaces. I'm assuming that a database is composed of tablespaces.
>Is this true.

There is no concept of "multiple databases" in Oracle. You log into one database to do work. If you want to work with a different DB, you log out of the current and log into another DB. These DBs share _no_ resources - they use different datafiles, memory resources, etc.

Remember, the database is the file part, in Oracle terminology.

Starting at the OS level:

A Database is made up of datafiles.
A database consists of one or more datafiles. A datafile belongs to one and only one database.

Datafiles make up tablespaces.
A datafile can belong to one and only one tablespace. A tablespace can consist of one or more datafiles.

Tablespaces contain database objects (tables, indexes, rollback, etc). Database objects reside in one and only one tablespace. Tablespaces can contain zero or more database objects.

>Bottom line, I'm hung up on where the database is (I know that sounds
>weird), how to view their properties, how to modify them or create them
>in the first place. The highest level abstraction in the SVRMGRM GUI
>seems to be the tablespace.

The instance that corresponds to a database is configured via the initSID.ora file. Look in your $ORACLE_HOME/dbs directory for this file. Modifications can be done through this init.ora, which is read on startup, through svrmgrm/svrmgrl, Oracle Enterprise Manager, etc.

I would recommend sitting down with the Oracle Concepts manual and if not reading it cover to cover (good idea), at least going through it good.

>Thanks for any help you can give.

I don't know if that was help or harm - hopefully someone will correct all the errors I've made in the above. But feel free to contact via e-mail, if you have other questions.

-- 
/(o\ Nathan D. Hughes
\o)/ nhughes_at_umich.edu