Using OMF to simplify database management

Oracle9i brings a number of exciting new features, one of which is Oracle's automated management files at the operating system level-Oracle Managed files (OMF). Before oracle9i occurs, the DBA must manually remove the data file (datafile) when the tablespace is unloaded and carefully examine the location of the file before creating a new table space.

To understand how OMF works, let's first define a new parameter called Db_cteate_file_dest.

Alter system set db_create_file_dest= '/u01/oradata/prod ';

Once the Db_cteate_file_dest parameter is set, we can create the table space without specifying the filename.

Createtablespace
Omf1
DataFile size 100m
Locally managed;

After the file is created, Oracle can assign and name the files. Oracle OMF uses the following naming transformation conventions. The default file size is 100M and is named in the following format:

where
%u is a unique 8 digit code
%g is the log file group number
%t is the tablespace name

Controlfiles Ora_%u.ctl
Redo Log Files Ora_%g_%u.log
Datafiles ora_%t_%u.dbf
Temporary datafilesora_%t_%u.tmp

The Oracle9i OMF tool also has a new warning log message (alert log) that tells us when the OMF data file has changed. Here is an example of a warning log.

Fri Mar 23 01:44:46 2001
CREATE tablespace omf1 datafile SIZE 10M autoextend off
Fri Mar 23 01:44:47 2001
Created Oracle Managed FILE/DATABASES/ED25/OMF1/ORA_OMF1_XCP6RG84.DBF
Completed:create tablespace omf1 datafile SIZE 10M autoexte
Fri Mar 23 01:45:45 2001
Drop Tablespace OMF1
Fri Mar 23 01:45:45 2001
Deleted Oracle Managed FILE/DATABASES/ED25/OMF1/ORA_OMF_XCP6RG84.DBF
Completed:drop tablespace OMF1