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Re: Database vs. Tablespace vs. Datafiles

From: Gary Gapinski <glg_at_apk.net>
Date: Fri, 21 May 1999 07:30:09 -0400
Message-ID: <374543C1.7E97E5D4@apk.net>


Hello, Jon/Greg:

When a database is created, a tablespace called SYSTEM is gratuitously created to hold the data dictionary. A datafile must be specified for this tablespace's residence. Additional "datafiles" must be specified for logs, control files, and so forth.

Tablespaces are just areas in which objects can be located. One can have as many as one wishes.

Tablespaces are comprised of one or more datafiles. What Oracle calls "datafiles" are manifest at the OS level as files within a file system, or just chunks of disk space (so-called "raw" devices"). The Oracle software manages the content of the tablespace, and does not wish any other programs to muck about with the associated datafiles.

After database creation (the CREATE DATABASE directive), additional tablespaces (and datafiles thereof) are created (the CREATE TABLESPACE directive) as one wishes. Customarily, a tablespace is created for rollback segments, another for temporary objects, another for tables, another for indices, and others at the whim of the DBA. Separate tablespaces for objects of a certain ilk makes it easier to manage the database.

Thereafter, users are created, and objects are created by or on behalf of users. An object's tablespace of residence is specified at the time of its creation, or is implied by the DEFAULT TABLESPACE attribute of the owning user. Users must specifically, or indirectly by a role, be granted QUOTA on tablespaces in which their objects will be created.

HTH Regards,

Gary

PS: lose the sig. Received on Fri May 21 1999 - 06:30:09 CDT

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