[Info-vax] Use of logical names other than I/O redirection

[Jonathan]

25 years ago or so I implemented query queues using logicals (and locks.)  I thought the implementation would be replaced at some point, but it's still in use.  Description from the sources:

!	Query/Reply queues implemented using logical tables
!
!	The data for each queue is stored in individual logicals in
!	a logical table created for the queue in the system logical
!	table directory.
!
!	The logical table has four kinds of logical.
!	Logical:		Contains:
!	VERSION			current version of queue.  The value is
!				  a hexadecimal time string.
!	<version>_TAIL		the index of the last item in the queue.
!				  The value is a decimal string.
!				  Item numbering starts at 1
!	<version>_ENTRY_<n>	The state of the <n>th item in the queue.
!				  The states are QUERY and REPLY and describe
!				  the contents of the buffer.
!	<version>_BUFFER_<n>	The buffer holding the data for the
!				<n>th item in the queue.  This logical
!				may have multiple translations.  The data
!				is the concatenation of all the translations.
!
!	Together the _<n> suffixed logicals constitute an item in the queue.
!
!	The reason for the separate queue entry and buffer logicals:
!	   1) The upper limit on a logical value is 255 bytes.
!	   2) Buffers need to be larger than 255 bytes.  The required
!		larger buffers are implemented as logical arrays (search lists.)
!	   3) Creating a logical array is not an atomic operation.  A reader
!		may see a partial array.
!	   4) The logical arrays are created before the queue entries that
!		point to them.	The queue entries are created in an atomic
!		operation.
!
!	The version is used to avoid problems when a querier sets a timeout
!	long enough for the replier to shutdown/die and restart.  The replier
!	creates a new queue, destroying any old queue.	If there were no
!	versions the querier might read someone-else's later query.

Jonathan