NAME
dcc — control read and write caching for HP SCSI disk array drives
SYNOPSIS
dcc
[options]
[drive_list]
device_file
DESCRIPTION
dcc
displays or changes the read-ahead caching status, and write-immediate
reporting status of selected drives on the
HP SCSI
disk array referenced by
device_file.
Options
- -d
Display only. Displays the read-ahead caching and write immediate reporting
status of all selected drives on the
HP SCSI
disk array. For
HP C2430
disk array devices, the number and size of cache segments is
displayed.
This option cannot be used with any other option.
- -ron
Read on. Enables read-ahead caching on all selected drives of the
HP SCSI
disk array. Can be used in combination with one of the
write-immediate reporting options.
- -roff
Read off. Disables read-ahead caching on all selected drives of the
HP SCSI
disk array. Can be used in combination with one of the
write-immediate reporting options.
- -won
Write on.
Enables write-immediate reporting on all selected drives of the
HP SCSI
disk array. Can be used in combination with one of the
read-ahead caching options.
- -woff
Write off.
Disables write immediate reporting on all selected drives of the
HP SCSI
disk array. Can be used in combination with one of the
read-ahead caching options.
- -snum_segments
Set the number of cache segments. This option is unique to the
HP C2430
disk array.
The disk mechanism cache can be segmented into 1, 2, 4, 8 or 16 segments.
The default is 2 segments.
This option cannot be used with other options.
- drive_list
Specify a set of drives.
If this optional list is absent,
the default set of affected drives is all drives attached to the controller.
The list is in the form
cXiY
,... where
X
(a decimal number) represents
SCSI
channel number,
and
Y
(a decimal number) represents the
SCSI ID
of the drive.
Multiple drives in the list are separated by commas.
RETURN VALUE
dcc
returns the following values:
- 0
Successful completion.
- -1
Command failed (an error occurred).
ERROR MESSAGES
Errors can originate from problems with:
SCSI
(device level) communications
Error messages generated by dcc:
- usage: dcc options [cXiY,...] <special>
An error in command syntax has occurred.
Enter command again with the required arguments, in the order shown.
- dcc: Arg out of range
One of the arguments is larger than its allowed maximum value
(or smaller than its allowed minimum value), or
is incorrect in form. Check the size, and form of each argument
and make appropriate corrections.
- dcc: device busy
To ensure that
dcc
does not modify a disk array
that is being used by another process,
dcc
attempts to obtain exclusive access to the disk array.
If the disk array is already opened by another process
(for example, LVM — the Logical Volume Manager),
a
``device busy''
error message is returned by the driver.
To eliminate the
``device busy''
condition, determine what process has the device open.
In the case of LVM,
it is necessary to deactivate the volume group containing the array
before configuring the array (see
vgchange(1M)).
- dcc: LUN does not exist
The addressed
LUN
is not known to the array controller.
- dcc: LUN # too big
The
LUN
number, which is derived from the device special file name, is out of range.
- dcc: Not a raw file
Utilities must be able to open the device file for raw access.
- dcc: Not an HP SCSI disk array
The device is not an
HP SCSI
disk array.
- dcc: Transfer length error
The amount of data actually sent to (or received from) the device
was not the expected amount.
SCSI (device level) communication errors:
Sense data associated with the failed operation is printed.
Error messages generated by system calls:
dcc
uses the following system calls:
malloc(),
free(),
stat(),
open(),
close(),
read(),
write(),
and
ioctl().
Documentation for these
HP-UX
system calls contains information about the specific error conditions
associated with each call.
dcc
does not alter the value of
errno.
The interpretation of
errno
for printing purposes is performed by the system utility
strerror().
EXAMPLES
To display the status of read and write caching on all the drives of the
disk array
/dev/rdsk/c2t2d0
on a Series 700:
To enable write-immediate reporting on a list of drives on the
disk array
/dev/rdsk/c2t2d0
on a Series 800:
dcc -won c2i0,c1i0,c5i0,c4i1 /dev/rdsk/c2t2d0
To disable read caching and write-immediate reporting on the drives of the
disk array
/dev/rdsk/c2t4d0
on a Series 700:
dcc -roff -woff /dev/rdsk/c2t4d0
To set the number of cache segments on the
HP C2430
disk array
/dev/rdsk/c2t2d0
to 4 on a Series 800:
dcc -s 4 /dev/rdsk/c2t2d0
DEPENDENCIES
The HP C2425 and HP C2427 disk arrays are only supported on Series 700 systems
running HP-UX version 9.0X.
The HP C2430 disk array is supported on Series 700 and 800 systems runing HP-UX
versions 9.0X and 10.0X.
AUTHOR
dcc
was developed by HP.
