Oracle9i introduces a new feature that simplifies tablespace creation. This new feature, Oracle Managed Files (OMF), makes life easier for Oracle DBAs by removing the tedium from creating and managing Oracle data files.Before OMF, Oracle DBAs had to take several manual steps before adding a data file. A simple example of these steps follows, but note that you must know the location of the directory that contains the Oracle data files:create tablespace users_02add ‘c:oracleoradatadiogenesusers02.dbf’size 20m ;In this example, you must know the following information to create a new tablespace: The proper file location The proper filename The proper file size Prior to OMF, you needed to execute queries to get the filenames and file locations, interrogating the dba_data_files view to find the appropriate location for a new data file, as shown in Listing A..

Listing A

SQL> select file_name from dba_data_files; FILE_NAME ------------------------------------------------ C:ORACLEORADATADIOGENESSYSTEM01.DBF C:ORACLEORADATADIOGENESUNDOTBS01.DBF C:ORACLEORADATADIOGENESCWMLITE01.DBF C:ORACLEORADATADIOGENESDRSYS01.DBF C:ORACLEORADATADIOGENESEXAMPLE01.DBF C:ORACLEORADATADIOGENESINDX01.DBF C:ORACLEORADATADIOGENESTOOLS01.DBF C:ORACLEORADATADIOGENESUSERS01.DBF C:ORACLEORADATADIOGENES16K_TS.DBF

sidebarend–&gt

Listing A

SQL> select file_name from dba_data_files; FILE_NAME ------------------------------------------------ C:ORACLEORADATADIOGENESSYSTEM01.DBF C:ORACLEORADATADIOGENESUNDOTBS01.DBF C:ORACLEORADATADIOGENESCWMLITE01.DBF C:ORACLEORADATADIOGENESDRSYS01.DBF C:ORACLEORADATADIOGENESEXAMPLE01.DBF C:ORACLEORADATADIOGENESINDX01.DBF C:ORACLEORADATADIOGENESTOOLS01.DBF C:ORACLEORADATADIOGENESUSERS01.DBF C:ORACLEORADATADIOGENES16K_TS.DBF

Using the output of the previous query, the C:OracleOradataDiogenes directory is the proper location to add a new Oracle data file.Viewing tablespace information was also cumbersome. You had to write a query to join dba_tablespaces with dba_data_files to get the file sizes, as shown in Listing B.

Listing B

column file_name format a40 column tablespace format a15 column bytes format 999,999,999 select file_name, t.tablespace_name tablespace, bytes from dba_data_files d, dba_tablespaces t where t.tablespace_name = d.tablespace_name ;

The output is shown in Listing C.

FILE_NAME                                TABLESPACE             BYTES          

---------------------------------------- --------------- ------------          

C:ORACLEORADATADIOGENESSYSTEM01.DBF  SYSTEM           340,787,200          

C:ORACLEORADATADIOGENESUNDOTBS01.DBF UNDOTBS          209,715,200          

C:ORACLEORADATADIOGENESCWMLITE01.DBF CWMLITE           20,971,520          

C:ORACLEORADATADIOGENESDRSYS01.DBF   DRSYS             20,971,520          

C:ORACLEORADATADIOGENESEXAMPLE01.DBF EXAMPLE          159,907,840          

C:ORACLEORADATADIOGENESINDX01.DBF    INDX              26,214,400          

C:ORACLEORADATADIOGENESTOOLS01.DBF   TOOLS             10,485,760          

C:ORACLEORADATADIOGENESUSERS01.DBF   USERS             26,214,400          

C:ORACLEORADATADIOGENES16K_TS.DBF    TS_16K            10,485,760 

File size and naming standardsBefore OMF appeared, Oracle DBAs could create data files with any name they chose. While the file suffix was normally .dbf, the Oracle DBA was free to create any type of filename desired. For example, the following is a silly but legitimate Oracle command:create tablespace new_tsdatafile c:windowsProgram Filesautoexec.bat’ size 300m;As we can see from this example, allowing the developer to choose filenames and locations can have disastrous effects. When using OMF, files typically have a default size of 100 MB and are named using a format mask for the filename.Listing D presents the format mask that OMF uses when creating new data files. Listing D u% is a unique 8 digit code, g% is the logfile group number, %t is the tablespace name: Controlfiles ora_%u.ctl Redo Log Files ora_%g_%u.log Datafiles ora_%t_%u.dbf Temporary Datafiles ora_%t_%u.tmp

Listing D

u% is a unique 8 digit code, g% is the logfile group number, %t is the tablespace name: Controlfiles ora_%u.ctl Redo Log Files ora_%g_%u.log Datafiles ora_%t_%u.dbf Temporary Datafiles  ora_%t_%u.tmp

sidebarend–&gtWith OMF, tablespace creation syntax is simplified, and it becomes easy to allocate a new tablespace:SQL> create tablespace new_ts;Tablespace created.Now that the benefits of OMF are apparent, I’ll examine the process for installing and using it. To use OMF, you must set the db_create_file_dest parameter. Once this is set, OMF is installed and tablespace creation becomes super easy:SQL> alter system set db_create_file_dest=’c:oracleoradatadiogenes;System altered.SQL> create tablespace test;Tablespace created.Now I’ll look at the filename, directory name, and size for the file that was created as a result of this command in Listing E.

FILE_NAME                                          TABLESPACE             BYTES

-------------------------------------------------- --------------- ------------

C:ORACLEORADATADIOGENESORA_TEST_YNJ2K200.DBF   TEST             104,857,600