LD WATCH LDan: lbn [,lbn...]

 	This command will set a watchpoint on a virtual or logical
 	blocknumber on the specified device. The lbn is ignored on
 	I/O functions which don't need an lbn (IO$_PACKACK for
 	example).

 	This makes it possible to let the driver take some actions
 	dependant of which lbn was accessed with a specified function-
 	code.

1    /FUNCTION

   /FUNCTION[=Keyword]

 	This qualifier specifies for which I/O function the watchpoint is set.

 	An optional keyword may be given:

 	FUNCTION=ALL		The watchpoint is set for all I/O functions

 	FUNCTION=READ		The watchpoint is set for IO$_READPBLK

 	FUNCTION=WRITE		The watchpoint is set for IO$_WRITEPBLK

 	FUNCTION=CODE=number	The watchpoint is set for the specified
 				I/O function code

 	The default is /FUNCTION=READ

2    /ACTION

   /ACTION[=Keyword]

 	This qualifier specifies the action to be performed when a valid
 	watchpoint is encountered. To be able to set a watchpoint one must
 	have either CMKRNL privilege, or be the owner of the device.

 	A watchpoint may have one action only: CRASH, ERROR or SUSPEND. An
 	exception is OPCOM, which may be specified in addition to any other
 	action for a specific watchpoint.

 	An optional keyword may be given:

 	ACTION=CRASH		This action will crash the system when a
 				matching lbn and function are found. Usage
 				of this keyword needs CMKRNL privilege.
 				The bugcheck type will be RSVD_LP.

 	ACTION=ERROR[=code]	This action will return a user-specified
 				errorcode when a matching lbn and function
 				are found. When the code is not specified
 				SS$_BUGCHECK will be returned.

 	ACTION=SUSPEND		This action will suspend the thread when a
 				matching lbn and function are found. This
 				enables one to look at the system with SDA
 				for further investigation. LD SHOW/WATCH will
 				show all processes waiting for a specific
 				watchpoint, while LD WATCH/RESUME will resume
 				the thread.

 	ACTION=OPCOM		This action will display an OPCOM message when
 				a matching lbn and function are found. The
 				message includes the process-id and the
 				imagename doing the request, the devicename,
 				the functioncode and the lbn. If the watchpoint
 				was a virtual one (/FILE specified) then it
 				will show the vbn as well as the file-id of
 				the corresponding file.

 	The default is /ACTION=ERROR=676 (SS$_BUGCHECK)

3    /FILE

   /FILE=filespec

 	This qualifier will enable a virtual watchpoint on the specified
 	file. The parameter(s) will then be virtual blocknumbers of the
 	file.

4    /RESUME

   /RESUME

 	This qualifier resumes a suspended watchpoint. The parameter is the
 	watchpoint to resume. An alternate way to resume a watchpoint is
 	by /INDEX. If no parameter is specified then all suspended watchpoints
 	will be resumed.

5    /INDEX

   /INDEX=n

 	This qualifier enables watchpoint resume by index. The parameter
 	is the watchpoint number to resume.