LD TRACE LDan:

 	This command initializes the trace buffer for the specified
 	device. This buffer will log the following data for every
 	I/O request:

 	  o	Process ID
 	  o	Logical block number
 	  o	I/O request size
 	  o	I/O Function code
 	  o	I/O status block
 	  o	Timestamp from the start of the I/O request
 	  o	Timestamp from the end of the I/O request

 	The default size is 512 entries, the maximum is as big
 	as pool will allow.

 	The allocated size from pool will be:

 		PoolSize (in Bytes) = (N * 88) + 12

 	where N equals the number of entries.

1    /ACCURATE

 	This qualifier was used in the past to allow accurate timing
 	measurements. A new method of collecting the timing has been
 	used which always collects the accurate samples, making this
 	qualifier obsolete. It will be ignored.

2    /ALL

 	The first use of this qualifier is to enable all data to be
 	logged for tape devices. This means that besides the tape I/O
 	also the underlaying requests to disk are logged.

 	The second use is in combination with /STOP to stop all
 	processes which are currently tracing data for all LD devices.

3    /FDT

 	Allows FDT routine access to be traced. This is a form of
 	preprocessing which every I/O request goes through. This qualifier
 	causes usage of additional entries in the tracebuffer for almost
 	every I/O request, hence it is made optional.

 	This qualifier will only work on Alpha.

4    /RESET

 	When this qualifier is specified the tracebuffer will be reset.
 	All data currently in the buffer will be lost.

5    /SIZE

  /SIZE[=number_of_entries]

 	Specifies the size of the tracebuffer. The default size
 	is 512 entries.

6    /STOP

 	This qualifier can be used to stop another process which has
 	issued a SHOW/TRACE/CONTINUOUS command. The devicename must
 	be specified (unless /ALL was given). If the trace was started
 	by a process in the same UIC group, GROUP privilege is needed.
 	If the process belongs to another UIC group, WORLD privilege
 	is needed.