You can use nonstop processes (NWP) in order to increase your system reliability. A specific license is required for this purpose. In nonstop operation, only the WPs of one computer are active. The processes of a different computer (nonstop processes) are available upon request. If the primary computer that includes the active WPs fails, the nonstop processes take over their role. As opposed to a usual parallel operation, the system configuration NonStop Server does not use the WPs of all computers. The WPs of ony computer are always in the mode "hot standby."
The System Overview lists all server processes of the AE system. Type "N" processes are nonstop processes and are displayed with the symbol.
The following example describes the functionality of nonstop processes in more detail:
The server processes of an AE system are located on two computers. A work process of computer A logs on first and obtains the status of the primary work process (PWP). All other server processes of computer A are set active. All work processes of computer B automatically become nonstop processes. If computer A goes offline, the nonstop processes become active work processes, and one of them obtains the status of a primary work process.
- The license has automatically the effect that a server process changes to NonStop Server mode. No other specifications are required to install and configure the Automation Engine.
- The starting order of the server processes is decisive for the classification of server processes. The server processes that start first are set active. The other computer, including its server processes, becomes the NonStop Server.
- Only work processes can become nonstop processes. Communication processes are always active. At least one communication process should be available on the computer with the nonstop processes in order to ensure that the nonstop processes can proceed.
- The NonStop Server takes over processing if it does not receive any message from the primary work process for a specified period of time. This time span can be defined in the Automation Engine's INI file using the parameter alivetimeout= (section [TCP/IP]). Automic strongly recommends changing the default value only if necessary.
Use the script element GET_UC_SETTING in order to retrieve a server process type. Return code "N" is supplied if the server process is a nonstop process.