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 dcc(1M)							     dcc(1M)




 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



 Hewlett-Packard Company	    - 1 -   HP-UX Release 11i: November 2000






 dcc(1M)							     dcc(1M)




			      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:

	   +  dcc

	   +  SCSI (device level) communications

	   +  system calls

    Error messages generated by dcc:
      usage: dcc options [cXiY,...] <&lt&lt&lt;special>&gt&gt&gt;
	   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.




 Hewlett-Packard Company	    - 2 -   HP-UX Release 11i: November 2000






 dcc(1M)							     dcc(1M)




      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:

	   dcc -d /dev/rdsk/c2t2d0

      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




 Hewlett-Packard Company	    - 3 -   HP-UX Release 11i: November 2000






 dcc(1M)							     dcc(1M)




      dcc was developed by HP.





















































 Hewlett-Packard Company	    - 4 -   HP-UX Release 11i: November 2000