VERITAS Storage Foundation 4.1 Oracle Administrator's Guide
Chapter 5, Using VERITAS Extension for Oracle Disk Manager
Prerelease 8 September 2005, 8:54am Oracle Disk Manager and Oracle Managed Files
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Oracle Disk Manager and Oracle Managed Files
Oracle9i or later offers a feature known as Oracle Managed Files (OMF). OMFs manage datafile
attributes such as file names, file location, storage attributes, and whether or not the file is in use by
the database. OMF is only supported for databases that reside in file systems. OMF functionality is
greatly enhanced by Oracle Disk Manager.
The main requirement for OMF is that the database be placed in file system files. There are
additional prerequisites imposed upon the file system itself. OMF is a file management feature that:
◆ Eliminates the task of providing unique file names
◆ Offers dynamic space management by way of the tablespace auto-extend functionality of
Oracle9i or later
OMF should only be used in file systems that reside within striped logical volumes, which support
dynamic file system growth. File systems intended for OMF use must also support large, extensible
files in order to facilitate tablespace auto-extension. Raw partitions cannot be used for OMF.
By default, OMF datafiles are created with auto-extend capability. This attribute reduces capacity
planning associated with maintaining existing databases and implementing new applications. Due
to disk fragmentation that occurs as the tablespace grows over time, database administrators have
been somewhat cautious when considering auto-extensible tablespaces. Oracle Disk Manager
eliminates this concern.
When Oracle Disk Manager is used in conjunction with OMF, special care is given within
VERITAS Extension for Disk Manager to ensure that contiguous disk space is allocated to
datafiles, including space allocated to a tablespace when it is auto-extended. The table and index
scan throughput does not decay as the tablespace grows.
How Oracle Disk Manager Works with Oracle Managed Files
This section contains examples illustrating the relationship between Oracle Disk Manager and
OMF.
Note Before building an OMF database, you need the appropriate init.ora default values.
These values control the location of the SYSTEM tablespace, online redo logs, and control
files after the CREATE DATABASE statement is executed.