RPC Communications - v1.0 Spring 1994, v1.1 Summer 1994

• Global sections imposed restrictions on structure of database and are inconvenient for a dynamically changing database.

  Use dynamic database and RPC methodology.

• RPC version consisted of (see Fig. ):
  • Server process maintaining configuration.
  • Client applications using RPCs to request changes and retrieve data. Maintain duplicate of database.

    
  Figure: CAMP Distributed Design using RPCs
  

• Use ONC (Sun) RPCs (seen as most portable at the time). MultiNet provides unsupported library for VAX/VMS.
• RPC XDR routines optimized to reduce overhead of client updates.
• Variables organized like a (Unix) directory tree (see Fig. ), with the following new types (besides the ``Numeric" type):
  • ``String" - editable character string.
  • ``Selection" - selection of strings.
  • ``Structure" - organize related variables below this variable.
  • ``Instrument" - top variable for an instrument.
  • ``Link" - link to variable in another instrument, allows pseudo-instruments.

    
  Figure: Sample CAMP Variable List - tree-like organization
  

• Some instruments can use either RS-232-C or GPIB.

  Remove interface-specific information from instrument driver.