Enabling Concurrent I/O


Enabling Concurrent I/O
Prev	Enabling and disabling Concurrent I/O	Next

Because you do not need to extend name spaces and present the files as devices, you can enable Concurrent I/O on regular files.

Warning:

If you use the -o cio option with the mount command to mount your primary database file systems, the Concurrent I/O settings will not be preserved when using Database FlashSnap commands or the command.

Before enabling Concurrent I/O, review the following:

Prerequisites	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.
Usage notes	When a file system is mounted with the Concurrent I/O option, do not enable Quick I/O. DB2 will not be able to open the Quick I/O files and the instance start up will fail. Do not use any Quick I/O tools if the database is using Concurrent I/O. See the (1M) manual page for more information about mount settings.

To enable Concurrent I/O on a file system using mount with the -o cio option

Mount the file system using the mount command as follows:
```
# /usr/sbin/mount -F vxfs -o cio special /mount_point
```
where:
- special is a block special device
- /mount_point is the directory where the file system will be mounted.

For example, to mount a file system named /datavol on a mount point named /db2data:

# /usr/sbin/mount -F vxfs -o cio /dev/vx/dsk/db2dg/datavol \
/db2data

To enable Concurrent I/O on a DB2 tablespace when creating the tablespace

Use the db2 -v "create regular tablespace..." command with the no file system caching option.
Set all other parameters according to your system requirements.

To enable Concurrent I/O on an existing DB2 tablespace

Use the DB2 no file system caching option as follows:
```
    # db2 -v "alter tablespace tablespace_name no file system caching"
```
where tablespace_name is the name of the tablespace for which you are enabling Concurrent I/O.

To verify that Concurrent I/O has been set for a particular DB2 tablespace

Use the DB2 get snapshot option to check for Concurrent I/O.
```
# db2 -v "get snapshot for tablespaces on dbname"
```
where dbname is the database name.
Find the tablespace you want to check and look for the File system caching attribute. If you see File system caching = No, then Concurrent I/O is enabled.