When using a remote session in a client application to connect to an ElevateDB Server, ElevateDB uses the operating system TCP/IP protocol support to perform all required communications to and from the ElevateDB Server. The TCP/IP protocol guarantees that any data stream sent either to or from an ElevateDB Server will arrive as a complete stream in the exact form that was sent. However, there is no way to guarantee that a given connection will be maintained indefinitely and not be interrupted by hardware or software issues that cause the connection to be lost. This article discusses how ElevateDB can handle such situations and how you can configure ElevateDB to optimally deal with them in the manner that you wish.



Configuring the ElevateDB Server

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Before you can establish a remote session connection to an ElevateDB Server, you must first configure and start the ElevateDB Server. You will find out more general information on this in the Starting and Configuring the ElevateDB Server topic in the ElevateDB SQL Manual.

ElevateDB uses timeout settings with both remote sessions and the ElevateDB Server to control how long each end of a connection will sit idle waiting for a request or response from the other end of the connection. For the ElevateDB Server, this value can be configured via the configuration .ini file and the following configuration entry:


Once a timeout is reached for a session on an ElevateDB Server, the session is disconnected and the dead session cleanup process begins for that session. There are three configuration entries on an ElevateDB Server that control how and when such sessions are removed automatically by the ElevateDB Server:


After all of these configuration entries are modified as desired, you can go ahead and start the ElevateDB Server so that you can proceed to test various configuration options for remote sessions in the client application.

Configuring Remote Sessions

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For a remote session, the connection timeout value can be configured as follows:


The default value is 180 seconds, or 3 minutes.

This timeout setting is important because it controls how long client applications wait for a response from an ElevateDB Server before an exception is raised. Once a timeout is reached for a remote session, the following occurs:


To prevent a session from timing out on an ElevateDB Server, a remote session can be configured to ping the ElevateDB Server every x number of seconds. A ping is simply a request sent to an ElevateDB Server that resets the timeout period for the session, and prevents it from ever timing out. Pinging can be configured as follows:


The default value is False for enabling pinging, and 60 seconds, or 1 minute, for the ping interval.


After you have configured a remote session and need to establish a remote session connection to an ElevateDB Server, the following information will help with that process:


Remote Session Reconnections

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By default, ElevateDB will always try to reconnect a remote session if it detects that the session does not currently have an active connection to the ElevateDB Server, either due to a timeout (see above) or some other issue that has caused a disconnection. If a remote session is configured to use pinging, and the pinging is configured properly, then reconnections will not be necessary. However, if pinging is not being used, then a remote session can possibly exist on the ElevateDB Server in a disconnected state ("dead") for quite a while before it is removed. As long as the session has not been removed by the ElevateDB Server the remote session can reconnect to it. ElevateDB gives you an opportunity to control this process as follows:


Using a reconnection event handler can be useful for situations where you are shutting down a client application due a communication problem with the ElevateDB Server or some other issue and you don't really care if the remote session can no longer communication with the ElevateDB Server. In such a case, setting the Continue parameter/property to False and the StopAsking parameter/property to True will allow ElevateDB to shut down the remote session without triggering the reconnection event any further, regardless of whether the remote session has problems getting a response from the ElevateDB Server.

Summary

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ElevateDB offers a fairly granular amount of control over how connections are handled for remote sessions. This will allow you to choose the connection model that fits your needs, while still retaining the option of switching to a different model in the future as your needs may change.

Hopefully we've been able to give you a little better understanding of how remote sessions and connections work in ElevateDB. As always, if you have any questions at all, please feel free to post them in the ElevateDB newsgroup here:

ElevateDB General Support Forum

This will allow everyone to share in any new ideas or comments that you may have regarding this article.

The next technical article will be entitled "Using Replication to Create an Incremental Backup of a Database", so look for it soon.