Veritas Storage Foundation 5.1 SP1 Advanced Features Administrator"s Guide (5900-1503, April 2011)

The Veritas Concurrent I/O feature removes these semantics from the read and
write operations for databases and other applications that do not require
serialization.
The benefits of using Concurrent I/O are:
■ Concurrency between a single writer and multiple readers
■ Concurrency among multiple writers
■ Minimalization of serialization for extending writes
■ All I/Os are direct and do not use file system caching
■ I/O requests are sent directly to file systems
■ Inode locking is avoided
Enabling and disabling Concurrent I/O
Concurrent I/O is not turned on by default and must be enabled manually. You
will also have to manually disable Concurrent I/O if you choose not to use it in
the future.
Enabling Concurrent I/O for DB2
Because you do not need to extend name spaces and present the files as devices,
you can enable Concurrent I/O on regular files.
For DB2, you can enable an entire file system to use Concurrent I/O or you can
enable specific SMS containers to use Concurrent I/O. If you enable a specific SMS
container, the rest of the file system will use the regular buffer I/O.
Before enabling Concurrent I/O, review the following:
■ To use the Concurrent I/O feature, the file system must be a VxFS
file system.
■ Make sure the mount point on which you plan to mount the file
system exists.
■ Make sure the DBA can access the mount point.
Prerequisites
For DB2, /mount_point is the directory in which you can put data containers of
the SMS tablespaces using the Concurrent I/O feature.
Note: This applies to both creating a new tablespace to use Concurrent I/O or
enabling an existing tablespace to use Concurrent I/O.
Improving database performance with Veritas Concurrent I/O
Enabling and disabling Concurrent I/O
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