• 3 Tier Solution

  

  This architecture is represented through:

  • Tier 1 - Client: Standard browser GUI interface;
  • Tier 2 - Server: NT or UNIX server running web server and TCP/IP connection to the mainframe;
  • Tier 3 - S390: Mainframe batch back-end with Rexx interface bridging the JES output queue or file content to Tier 2 via FTP/TCP/IP connection;

  Strengths

  • Standard user interface;
  • Separation of business and presentation logic;
  • Minimal disturbance of existing process - quick and easy setup;
  • Scalability through load distribution;
  • Availability through server redundancy;

  Weaknesses

  • Increases complexity of architecture;
  • Additional layer to maintain/support;
  • Requires TCP/IP connection for the mainframe;
  • Requires clients with TCP/IP connection and ability to run browser front end;
  
  
• 2 Tier Physical - 3 Tier Logical; OS390 Solution

  

  Here's the description of all three logical layers. Note that Tier 2 and Tier 3 both "live" on S390 box:

  • Tier 1 - Client: Standard browser GUI interface;
  • Tier 2 - Server: OS390 web server (Websphere);
  • Tier 3 - S390: Mainframe batch back-end with Rexx interface bridging the JES output queue or file content to Tier 2 via HFS or via FTP/TCP/IP transfer;

  Strengths

  • Standard user interface;
  • Separation of business and presentation logic;
  • Minimal disturbance of existing process - easy to setup after UNIX system services are configured;
  • No new hardware introduced;
  • Taking full advantage of already paid for hardware/software;

  Weaknesses

  • Increases complexity of architecture;
  • Unix system services setup/maintenance/support;
  • "All eggs in one basket" - no reports if mainframe goes down;
  • Scalability Vs. Performance issue;
  • Requires TCP/IP connection for the mainframe;
  • Requires clients with TCP/IP connection and ability to run browser front end;
  
  

• Javascript simulated under Win95/browser.

  This stand alone demo uses Javascript to simulate 3270 screens and programs behind it. It has no real functionality and works with static data.

• Perl simulated on Sun Solaris server.

  UNIX server based DEMO that can be found on our web site (http://www.bgdsoftware.com) is running Perl CGI to simulate back end Rexx execution.

• Rexx on OS390 in real life.

  Real application (MAINFRAME/Web Reports) runs Rexx scripts on S390.

All this shows you the potential for creativity and should hilight the fact that there are no miracle tools, but just the appropriate tools for the appropriate tasks. Always try to put all available tools in perspective and use the best tool or combination of tools to achieve your goals.