OMG (ORACLE managed files) in Oracle DBA

30 September, 2020


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OMG (ORACLE managed files)

……to create tablespaces without specifying data files location

    Table space    

  1. By introducing OMF from ORACLE 9i third party software need not maintain data file location anymore while creating the tablespace [OMF works regardless of what operating system behind]
  2. Simplifies the creation of database default values:

100 mb size

Auto-extend on

Locally managed TS

For data files                                                          01_mf_%t_%u.dbf

for log files                                                              01_mf_%g_%u.log

for control file                                                       01_mf_%u.ctl

g group member

mf managed files

t tablespace name

u unique id [8 characters]

  1. OMF reduces the corruption caused by administrators specifying the wrong file.

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Problems with OMF

We can not have multiple destinations for the datafiles, wherein in the case of log files, we can have multiple destinations.

[more I/Os]

We need not to maintain including contents and data files when dropping tablespace.  


Dba12 dbs]$ vi initrajpar.ora


SYS > sho parameter db_create_

SYS > create tablespace omf_1;

SYS> select file_name, tablespace_name from dba_data_files;

SYS> select file_name, bytes, tablespace_name from dba_data_files;

SYS> create tablespace omf_2 datafile size 20m;

SYS > create tablespace omf_3 extent management dictionary;                                                 [default local]

SYS > alter database add logfile group 3 size 4m;

[size 4m compulsory, else default is 100m]  

Database creation

Dba12 ~] $ export ORACLE _ SID = rajpar2

Dba12~] $ cd $ ORACLE_HOME/dbs

Dba12 dbs]$ cp init. Ora initrajpar2.ora

Dba12 dbs]$ vi intrajpar2. Ora






Core_dump_dest= ‘/disk4/oradata/pal2/cdump’

# undo_tablespace=undotbs


Dba12 dbs] $cd

Dba12 ~[$ sqlplus ‘/as sysdba’

SQL > startup nomount

SQL> create database rajpal2;              

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