Synchronizing the SQL database

The NETx Server does not synchronize the data that is stored within the SQL database. This includes trending values and test results of the NETx LaMPS module. However, it is possible to use synchronization features of the SQL database to provide a synchronization of the SQL data.

In principle, there are two possible scenarios for using an SQL database with a main / backup solutions.

Using single SQL database instance

Within this scenario, the main and backup server are using the same SQL server instance. The following figure shows the situation where the main server is online:

In this situation, the main server is connected to the SQL instance. The backup server is inactive and thus not connected to the SQL instance. Now, consider that the main fails and the backup server is getting active. In this case, the backup opens the connection to the single SQL instance:

This solution has the advantage that is easy to configure. In addition, only one SQL instance is required and no additional license fees for an SQL synchronization are necessary. The drawback is that the SQL instance is a single point of failure. If the SQL instance fails, the data is not available for BMS functions like reporting. To increase the reliability of a single SQL instance, hardware redundant server systems or fail-safe virtual machines can be used.

Using synchronization mechanisms of SQL database provider

Within the second scenario, two SQL instances are synchronized using the synchronization mechanism of the SQL provider. The following figure shows the basic principle:

Within this scenario, two physical SQL instances are synchronizing the SQL data. If one instance fails, the other takes over. After recovery, the data is synchronized again. 

The advantage of this solution is that there is also a full redundancy for the SQL data. From the NETx Server point of view, it looks like a single instance. Therefore, no special configuration efforts are necessary within the NETx Servers. The drawback is the time and effort to set up such an SQL cluster. Furthermore, additional license cost from the SQL provider may occur.

At the time of writing this document, successful tests with MS SQL Server synchronization have been done. However, for MS SQL Server synchronization, additional license costs from Microsoft will occur. For MariaDB, no information is available, yet.