Server Emulation

Geo SCADA Expert includes a Server Emulation feature that enables you to choose a version of Geo SCADA Expert for the server to emulate. This enables clients that are running different versions of Geo SCADA Expert to continue to be used for displaying and/or editing documents. Server Emulation also enables requests to be proxied to the Main server by a Standby server that is running either the same or an older version of Geo SCADA Expert software to the Main server. Such a difference in software versions might occur while upgrading a multi-server system. Server Emulation is intended to be used as a temporary measure while you upgrade your system from an older version of Geo SCADA Expert software. Once you have completed the upgrade and verified that it is successful, you then turn the Server Emulation off. However, you only do this once all of the clients that you intend using to display and/or edit documents (such as Mimics and Trends) have been upgraded to use the same version of Geo SCADA Expert software.

This is because database files are stored in a format that is version-specific (to accommodate the database items and properties that are supported by the particular version of Geo SCADA Expert software). Geo SCADA Expert clients can only display documents (such as Mimics and Trends) that have been created and saved using a version of Geo SCADA Expert up to, and including, the version that those clients are currently running. If your system is likely to have a mixture of old and new clients while it is being upgraded and you want all of those clients to continue to be able to access documents, use Server Emulation.

When using the Server Emulation feature, you set the server to emulate the version of Geo SCADA Expert software that is compatible with the oldest clients on your system (the clients that run the oldest version of Geo SCADA Expert). The feature enables the older clients to access documents that are created and edited on newer clients.

If a user attempts to display a document that has been saved in a version that is not supported by a client, the document display will show an 'unsupported file format' diagnostics message. This means that the document has been saved on a client that runs a later version of Geo SCADA Expert. (The client showing the diagnostics message runs an older version of Geo SCADA Expert than the client on which the document was saved). You can rectify this problem by using the Save All Documents feature (see Converting Unsupported Files into Supported Files).

If, during the upgrade process, Database Emulation is enabled in addition to Server Emulation, users will be able to perform configuration activities as described above. The same applies if you are upgrading the version of Geo SCADA Expert in a Lone Server architecture, regardless of whether Database Emulation is enabled.

A restriction might apply during the upgrade process if your system includes clients that connect to the database via a Standby server. If you use Database Emulation or Server Emulation, or you delay upgrading those clients until all of the servers have been upgraded, users will be able to continue to perform configuration-related changes on the clients. For more detail, see Clients on Standby Servers - Restrictions that Apply during an Upgrade. A restriction applies if you do not use Database Emulation or Server Emulation and also upgrade the clients on an upgraded Standby server while the Main server continues to run an older version of software. With such a scenario, ensure that users are aware that they will be unable to perform configuration-related changes on the clients that are on those Standby servers until the upgrade has been completed on all of the servers on the system. This is by design, as servers cannot proxy requests to older server versions. Any requests from a Standby server that are proxied to the Main server for processing are rejected while the Main server is running an older version of Geo SCADA Expert software than the Standby server. This includes configuration-related requests. Attempts to proxy such requests will result in a diagnostic message such as:

Cannot proxy request to older server version.

For more information, see Preparing to Upgrade Geo SCADA Expert in the Geo SCADA Expert Installation Guide.

In the rest of this section, we explain:

• Setting a Server to Emulate a Software Version
• Converting Unsupported Files into Supported Files.