Veritas File System 5.1 SP1 Administrator"s Guide (5900-1499, April 2011)

as to which regions or blocks of a mirrored datafile to resync after a system crash.
Oracle Resilvering avoids overhead from the VxVM DRL, which increases
performance.
Oracle Disk Manager reduces administrative overhead by providing enhanced
support for Oracle Managed Files. Veritas Extension for Oracle Disk Manager has
Quick I/O-like capabilities, but is transparent to the user. Unlike Veritas Quick
I/O, files managed using Veritas Extension for Oracle Disk Manager do not require
special file naming conventions. The Oracle Disk Manager interface uses regular
database files. If you are upgrading to Oracle10g or later, you should convert from
Quick I/O to Oracle Disk Manager.
Database administrators can choose the datafile type used with the Oracle product.
Historically, choosing between file system files and raw devices was based on
manageability and performance. The exception to this is a database intended for
use with Oracle Parallel Server, which requires raw devices on most platforms. If
performance is not as important as administrative ease, file system files are
typically the preferred file type. However, while an application may not have
substantial I/O requirements when it is first implemented, I/O requirements may
change. If an application becomes dependent upon I/O throughput, converting
datafiles from file system to raw devices is often necessary.
Oracle Disk Manager was designed to work with Oracle10g or later to provide
both performance and manageability. Oracle Disk Manager provides support for
Oracle's file management and I/O calls for database storage on VxFS file systems
and on raw volumes or partitions. This feature is provided as a dynamically-loaded
shared library with which Oracle binds when it is loaded. The Oracle Disk Manager
library works with an Oracle Disk Manager driver that is loaded in the kernel to
perform its functions.
If you are upgrading to Oracle10g or later, you should convert from Quick I/O to
Oracle Disk Manager.
The benefits of using Oracle Disk Manager are as follows:
■ True kernel asynchronous I/O for files and raw devices
■ Reduced system call overhead
■ Improved file system layout by preallocating contiguous files on a VxFS file
system
■ Performance on file system files that is equal to raw devices
■ Transparent to users
■ Contiguous datafile allocation
Using Veritas Extension for Oracle Disk Manager
About Oracle Disk Manager
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