Oracle Cluster File System (OCFS) Tips

Oracle Cluster File System (OCFS) is a shared file system designed specifically for Oracle Real Application Clusters. OCFS eliminates the requirement for Oracle database files to be located on the raw devices in Linux RAC cluster and Windows RAC cluster.

OCFS is released under the GNU General Public License (GPL). The source code for the binaries shipped with the RPM's are directly available in the source RPMS (.src.rpm) for reference and compliance. Oracle will only formally support the binary RPM's compiled by Oracle and downloadable for Red Hat Advanced Server or United Linux. Oracle provides OCFS product support to customers that already have an Oracle support license.

For Linux and Windows

With the active support from open source community, Oracle has developed the cluster file system (OCFS) for use in Red Hat Linux and United Linux, and released it as an open source. It is available in the form of RPM packages. Users can download it for free. OCFS only supports Oracle data files, redo log files, and control files. It is not a general-purpose file system. It does not support a shared Oracle Home at least not until Version 2 is released.

OCFS requires the use of the operating system’s o_direct compile-time flag to get direct I/O. I/O must be performed through aligned buffers with 512 byte (or multiples thereof) buffer offsets. These are details the Oracle server takes care of. The Oracle RAC database manages all the difficult concurrency issues and maintains the data integrity of the application just as it does when using raw partitions.

The OCFS version for Windows NT/2000 is also. OCFS for Windows does support a shared Oracle Home.

OCFS2 is the latest version of the Oracle Cluster File System software. While OCFS Version 1 was designed specifically for Oracle Database files, OCFS Ver 2 supports a shared ORACLE_HOME installation also.

New features of the OCFS Version 2 include:

Shared ORACLE_HOME
Improved performance of metadata operations (space allocation, locking, etc).
Improved metadata caching.
Improved data caching (for files such as oracle binaries, libraries, etc)
Network based DLM is used by default.
Improved journaling / node recovery - we now use the Linux Kernel "JBD" subsystem
Keep the same performance for Oracle data files as OCFS1.
CDSL for node specific files

OCFS For Linux

Oracle has developed the cluster file system (OCFS) for use in Red Hat Linux and United Linux, and released it as an open source. It is available in the form of RPM packages. Users can download it for free. OCFS only supports Oracle data files, redo log files, control files, and server parameter files. It is not a general-purpose file system and therefore does not support a shared Oracle Home.

OCFS requires the use of the operating system’s o_direct compile-time flag to get direct I/O. I/O must be performed through aligned buffers with 512 byte (or multiples thereof) buffer offsets. These are details the Oracle server takes care of. The Oracle9i RAC database manages all the difficult concurrency issues and maintains the data integrity of the application just as it does when using raw partitions.

OCFS For Windows

The OCFS version for Windows NT/2000 is available on CD with the latest Oracle9i Release 2 (9.2.0.1). OCFS can also be downloaded through OTN: http://otn.oracle.com/software. OCFS for Windows does support a shared Oracle Home.

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