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Database file types

Database file types

Nov 30, 2012

Dbvisit Standby recognises four database file types that are treated differently during creation of the standby database:

  • Regular filesystem files (FS)

  • Filesystem Oracle Managed Files (OMF)

  • ASM files with fully qualified system name (FQSN)

  • ASM aliases (ALIAS)

Regular filesystem files (FS)

These are regular database files that are stored in a filesystem. Example: /oracle/oradata/system.01.dbf


Filesystem Oracle Managed Files (OMF)

Oracle introduced the change to the filename format used for OMF in the second patch set for Oracle 9i Release 1 (9.0.1.2) and also in Oracle9i Release 2 (9.2). Prior to this fix OMF file names had the following format: 
File Type Format 

File Type 

Format

Example

Datafile

ora_%t_%u.dbf 

ora_tbs1_2ixfh90q.dbf

Tempfile

ora_%t_%u.tmp 

ora_temp1_6dygh80r.tmp

Redo log file

ora_%g_%u.log

ora_1_wo94n2xi.log

Control file

ora_%u.ctl

ora_cmr7t90p.ctl

Where:

     %t is the tablespace name (possibly truncated)

     %u is an eight character string that guarantees uniqueness

     %g is the online redo log file group number

A file was considered OMF if its base file name had:

  • an "ora_" prefix

  • and a ".dbf", ".tmp", ".log" or ".ctl" extension 

The new and current format for OMF file names on Windows and Unix-based systems is: 

File Type 

Format

Example

Datafile

o1_mf_%t_%u_.dbf

o1_mf_tbs1_2ixfh90q_.dbf

Tempfile

o1_mf_%t_%u_.tmp  

o1_mf_temp1_6dygh80r_.tmp

Redo log file

o1_mf_%g_%u_.log 

o1_mf_1_wo94n2xi_.log

Control file

o1_mf_%u_.ctl

o1_mf_cmr7t90p_.ctl

Where:

     %t is the tablespace name (possibly truncated)

     %u is an eight character string that guarantees uniqueness

     %g is the online redo log file group number

A file is now considered OMF if its base file name has:

  • a "o1_mf_" prefix

  • and a ".dbf", ".tmp", ".log", or ".ctl" extension

  • and an "_" character immediately preceding the extension 

ASM files with fully qualified system name (FQSN)

Every file created in ASM gets a system-generated filename, otherwise known as a fully qualified filename (FQFN). The fully qualified filename represents a complete path name in the ASM file system. An example of a fully qualified filename is:

+dgroup2/sample/controlfile/Current.256.541956473

ASM aliases (ALIAS)

 

+dgroup2/sample/controlfile/control01.dbf