VERITAS Storage Foundation 4.1 Oracle Administrator's Guide

Chapter 3, Using VERITAS Quick I/O
Prerelease 8 September 2005, 8:54am Using Oracle’s AUTOEXTEND With Quick I/O Files
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Using Oracle’s AUTOEXTEND With Quick I/O Files
Oracle supports an automatic extend feature that automatically grows a database file by a
prespecified amount, up to a prespecified maximum size.
For regular file system files, AUTOEXTEND works transparently, provided the underlying file
system has enough space. For example, suppose the current size of a database file emp.dbf is
100MB, but this file is expected to triple in size over time. To accommodate this growth using
AUTOEXTEND feature, you can specify the next size at 20MB and maxsize at 300MB. This
will automatically grow the file by 20MB until its size reaches 300MB. For example:
alter database datafile ’emp.dbf’ autoextend on next 20m\
maxsize 300m;
(See the Oracle Server SQL Reference Guide for more information about the alter database
command, as well as the next and maxsize parameters.)
Note You must have sufficient space on the underlying file system to AUTOEXTEND a file, and
the underlying storage device must be large enough to contain the new, larger file system.
For Quick I/O files or raw devices, AUTOEXTEND does not know how to grow the underlying
Quick I/O files or devices. Therefore, the Quick I/O file size must be large enough to accommodate
the new size before AUTOEXTEND can grow the datafile.
You can use AUTOEXTEND with Quick I/O files in the following ways:
◆ Preallocate the Quick I/O file to a size at least as big as the maximum growth size expected for
this database file.
Using this method, you would need to preallocate the Quick I/O file emp.dbf for the entire
300MB. The drawback is that this can unnecessarily lock up excess disk space. Raw devices
have a similar requirement.
◆ Monitor the free space available in the Quick I/O file, and grow the file as necessary with the
qiomkfile command.
Unlike raw devices, you can easily extend Quick I/O files online. Using this method, you can
monitor the free space available in the Oracle datafiles and use the qiomkfile command to
grow the Quick I/O files online as and when needed (typically when the file is about 80 to 90
percent full). This method does not require you to lock out unused disk space for Quick I/O
files. The free space on the file system is available for use by other applications.
Options
For the qiomkfile command:
-e Extends the file by a specified amount to allow Oracle tablespace resizing.