Re: Tablespaces, tables - could someone explain?

From: <mpir_at_compuserve.com>
Date: Mon, 08 Jun 1998 20:15:14 GMT
Message-ID: <6lhgoi$riv$1@nnrp1.dejanews.com>

Oracle is usually structured about as follows ____________ | DBMS |

-------------------------  | 
|------------------|---------------------|----------------------|------------
---------|--------------|  System  Rollbacks  AppData  Indexes	Tempspace 
Userspace  (Data Dict)	(Logs)	(Tables)  (ScratchPad)


Each of these 6 is  a Tablespace.  The tablespace consists of 1 or more data
files.	A tablespace can contain one or more tables and/or one or more

indexes (we'll ignore PL/SQL blocks and objects for this discussion).

The APPDATA and Index legs are sometimes broken up into several tablespaces, each holding the data appropriate for a given application.

When you got your first error, you did not need to create a new tablespace, just add another datafile to the tablespacespace you had.

As for the rollback segment, depending on the install process you used, typically only one rollback segment exists in the System tablespace. The DBMS uses this to manipulate the data dictionary. You need to have at least one, and maybe several (depending on the app and number of users) additional rollback segments. They are customarily placed in their own tablespace. You do not need to have one in each tablespace, and the current style doesn't do that, but in the old days is was more common. Rollbacks hold the before and after images of the rows modified in a transaction before the commit statement is issued. \ Your questions:

1- See above (I hope)

2- Just the data. The structure is in the data dictionary

3- It is better to separate them in different tablespaces and different disks, but for performance reasons, not for design/academic reasons.

4- The Oracle manual (V7.x Server Admin Appendix A, I believe) shows how to calculate space requirements.) There are also several spread sheets floating around.

5- See above (I still hope)

6- Use public rollback segments in shared/parallel database environments. Otherwise, it doesn't matter, as long as you have enought of them.

7 ctl-configuration and operational parameters (usually not human readable)

    log-log files
    sys- depends on platform and configuration

In article <357aee08.2639094_at_news.zeitung-online.net>,   stefan_at_westner.org (Stefan Westner) wrote:
>
> Hello,
>
> normally we use interbase but one of our customer wants to use oracle
> as db for our application.
>
> In interbase all jobs are quit simply - create the db, the tables,
> then the indices and start working.
>
> But otacle seems to be a bit complexer. Perhaps someone can tell me
> more:
>
> I run our db-create-table-script against oracle and all work fine
> under oracle 7.3.3 but under 7.3.4 I get some errors. The first error
> was that there was not enough room in the tablespace to create the
> table. I created a new tablespace tsp_a and create all tables in the
> tablespace tsp_a. When I commit the create-table-statements I got the
> error that I need a rollback-segment in the new tablespace.
>
> I create it then and set it online and my script ran without errors.
>
> Questions:
> 1.) What is a tablespace?
> 2.) What ist stored in a tablespace? The whole data or just the
> table-structure?
> 3.) If I have indexes and tables - is it better to create them in
> different tablespaces?
> 4.) the create tablespace takes several parameters about the size and
> the grow of the tablespace. How could I determine what size should I
> take for my data?
> 5.) What are rollback-segments?
> 6.) rollback segments can be public and private. What should I use
> under which circumstance?
> 7.) The tablespace is stored in a seperat file. What is stored in the
> ctl*, log* and sys*-file of an oracle-db?
>
> Thanks
>
> Stefan Westner
>

-----== Posted via Deja News, The Leader in Internet Discussion ==----- http://www.dejanews.com/ Now offering spam-free web-based newsreading Received on Mon Jun 08 1998 - 15:15:14 CDT