What are the drawbacks of Veritas Quick I/O and Cached Quick I/O. Does Oracle Support them . Do they work with RMAN.
All my datafiles are Veritas Quick I/O files only .Everything works great .I don't see any problem .Rman is also working without any probelm .
Yes Oracle recognizes Quick I/O. Some things to consider though (and this is taken from the Veritas Guide):
Quick I/O files, treated as raw devices by Oracle and Recovery Manager (RMAN), must
be backed up and restored the same 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 of 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. This can be
done 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
u 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.
u 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.
u If both the Quick I/O link name and the hidden file are intact, proceed to restore.
u If you attempt to restore to a Quick I/O file smaller than the required size, the restore
will fail with an Oracle error ORA-27069 (I/O attempt beyond the range of the file).
This is 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
would be encountered when attempting to restore Oracle datafiles built on raw
devices. In this case, delete the Quick I/O link and its hidden file, then recreate or
extend the file using qiomkfile.
One drawback is that with Quick I/O you cannot just issue a datafile resize command within the database. You have to resize using the Quick I/O interface then issue the resize command within Oracle (I don't remember the Veritas command at the moment). Remember, these files get treated as raw devices so you have the limitations of raw placed on you. Also, with Quick I/O Veritas does not recommend you doing this on the datafiles devoted to the TEMP tablespace.
[Edited by ramaral on 07-30-2002 at 02:53 PM]
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