OMG (ORACLE managed files) in Oracle DBA
OMG (ORACLE managed files)
……to create table spaces without specifying data files location.
- By introducing OMF from ORACLE 9i third party software need
not to maintain data file location any more, while creating the table space [OMF works regardless of what operating system behind]
- 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 table space name
u unique id [8 characters]
- OMF reduces the corruption caused by administrators specifying worong file.
Problems with OMF
We can not have multiple destinations for the datafiles, where in the case of log files, we can have multiple destination.
[more I/Os]
We need not to maintain including contents and data files when dropping tablespace.
DEMO ON OMF
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
Db_name=rajpal2
Instance_name=rajpar2
Db_create_file_dest=’/disk4/oradata/pal2’
User_dump_dest=’disk4/oradata/pal2/udump’
Background_dump_dest=’/disk4/oradata/pal2/bdump’
Core_dump_dest= ‘/disk4/oradata/pal2/cdump’
# undo_tablespace=undotbs
:wq
Dba12 dbs] $cd
Dba12 ~[$ sqlplus ‘/as sysdba’
SQL > startup nomount
SQL> create database rajpal2;