COMPARISON OF DATABASE MIRRORS TECHNOLOGY OF THE SELECTED DATABASE SYSTEMS FOR USE IN FAULT-TOLERANT INFORMATION SYSTEMS SOLUTIONS

The technological process control in the raw-material industry, which often operates in continuous mode 7x24, requires high robustness and safe operation. It was created a category of systems so-called fault-tolerant. The solution of system to be a fault-tolerant is in duplication of the entire system. In case of failure of any component of the production system the backup system takes control and ensures the continuous operation of the information (or control) system. A critical component of such solutions is to ensure the continuity of data in databases. Data taken from technological processes have the character of the time series and in case of failure missing data substantially disrupts the evaluation of balance of production. The solution to this problem is to use a database mirror technology for continuous on-line data mirroring between two instances of the database server. In the past we have used technology of Microsoft SQL Server mirroring solution with fault tolerant system for Darkov Coal Mine coal preparation plant. This year we have started research the possibility of using database technology mirror the world's leading manufacturers of database systems - Oracle, Microsoft SQL Server, MySQL and Cach - to simulate critical failures and determine behavior and immunity of systems against failure. Based on the tests we have an aim to propose the best solutions and best practices for deployment in fault-tolerant information systems for production control.