Re: Tablespaces, tables - could someone explain?

On 07-Jun-98 20:57:35 Stefan Westner wrote:

>Hello,

[...]

>Questions:
>1.) What is a tablespace?

Well, the name says it. ;-)
A tablespace is a space to store tables. In Oracle a tablespace consists off one or more datafiles. These are the physical OS files where the data is stored.

>2.) What ist stored in a tablespace? The whole data or just the
>table-structure?

The whole data is stored in the tablespace.

>3.) If I have indexes and tables - is it better to create them in
>different tablespaces?

This is a good idea because then you can put the different tablespaces on different disks to increase performance.

>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?

There are some formulars around to calculate the size of your data but I don't know them by heart. I filled a small test database and estimated the space the real data would consume.
Perhaps there are experts around to give you better advice on that topic.

>5.) What are rollback-segments?

Rollback segments are used to store altered data until the transaction is commited.

>6.) rollback segments can be public and private. What should I use
>under which circumstance?

AFAIK this does only matter if you have a parallel server installation or using multiple Oracle instances against the same database. I have not dived into that more deeply though...

>7.) The tablespace is stored in a seperat file. What is stored in the
>ctl*, log* and sys*-file of an oracle-db?

The ctl* are the controlfiles of the database. It contains the basic information about the database i.e. the paths of the datafiles and such stuff. (I think :-)
The log* are redo logfiles which contain the logging of the transactions performed with the database. When your system crashes, they enable you to use a backup of the datafiles ands the redo the transactions up to a certain point of time. (See abaout recovery in the manual) The sys* constitute the system tablespace which contains the data dictionary (a kind of diractory of every database ofject like tables, views, procedures etc.).

Note: all the above information is without warranty because written at home without Oracle or manuals at hand so might differ *slightly* from the real fatcs!

Hope that helps nevertheless,
Lothar

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