VERITAS Storage Foundation 4.1 Oracle Administrator's Guide

Appendix B, Using Third-Party Software to Back Up Files
Prerelease 8 September 2005, 8:55am Using Oracle RMAN to Back Up and Restore Quick I/O Files
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Using Oracle RMAN to Back Up and Restore Quick I/O Files
Quick I/O files are treated as raw devices by Oracle and Recovery Manager (RMAN) and must be
backed up and restored the same way as raw devices. A Quick I/O file consists of two components:
a regular file with space allocated to it and a link pointing to the Quick I/O interface for the file.
When a Quick I/O file is created with the qiomkfile command, the regular file with the
preallocated space is a hidden file. For example, dbfile points to .dbfile::cdev:vxfs:
and .dbfile is the hidden file with the space allocated. (These names are used in the examples
throughout this section.)
For backup, RMAN reads the Oracle datafile using the Quick I/O interface, but does not process or
store the special link between the hidden file with the allocated space (.dbfile) and the link to its
Quick I/O interface (dbfile, which points to .dbfile::cdev:vxfs:). This has implications
for the restore operation, as described in the rest of this section.
Because Quick I/O files are treated as raw devices, the Quick I/O file must exist and have the
necessary space preallocated to it before the file is restored using RMAN. Space can be
preallocated to the file when the file is created using the qiomkfile command. In this case, the
file can be restored using RMAN with no other special handling, and the file can be accessed after
the restore as a Quick I/O file:
◆ If both the Quick I/O link name and the hidden file are missing, use qiomkfile to
preallocate and set up the Quick I/O file.
◆ If either the Quick I/O link name or the hidden file alone exist, delete these files and recreate
the Quick I/O file of the required size using qiomkfile.
◆ If both the Quick I/O link name and the hidden file are intact, you may proceed to restoring the
file.
◆ If you attempt to restore a Quick I/O file and the original is smaller than the required size, the
restore will fail with an Oracle error ORA-27069 (I/O attempt beyond the range of the file).
The failure results because Quick I/O does not allow extending writes (in other words,
attempts to increase the size of a file by writing beyond the end of the file). This same behavior
is encountered when attempting to restore Oracle datafiles built on raw devices. If the restore
fails with the above error, delete the Quick I/O link and its hidden file, then recreate or extend
the file using qiomkfile.
Note The space needed for the Oracle datafile is the size of the datafile plus one Oracle block (as
specified by the init.ora parameter, db_block_size).