| Real-time database is the combination of real-time system and database technology. Real-time database has the characteristic of high speed, high data throughput and so on. It has been widely applied in automation field. Now, historical data storage is provided in most databases. Because of large numbers of acquisition points and short time period in control system, the amount of historical data is very large. Directly saving will cost vast space and make data transmission difficult.Data compression technology is imported into real-time database to resolve this problem. It can not only keep the characteristic of high speed, but also increase the capacity of database. There are two kinds of data compression technologies in real-time database, exception reporting compression method and boxcar-back slope algorithm. These compression methods will sacrifice data accuracy and can't achieve high compression radio, so they aren't suitable for high accuracy demand.Data compression technology is introduced into real-time database in this paper, which can realize lossless and high-performance compression. First, real-time database and data compression technology are introduced, then the principle of common data compression algorithm are explained, at last the design scheme of data compression algorithm is introduced, which is generated based on analyzing the characteristic of historical data and many kinds of data compression algorithms. Historical data in real-time database consists of three portions: data value, time stamp and quality code, which all have different characteristics. In order to achieve better compression performance, the compression algorithms are specially designed by sort. The RTLZ compression algorithms are derived from common compression algorithms LZ78 and LZW, achieve very high performance. The algorithm advances the performance of database in real-time performance and capability.In the end, the foreground of the compression algorithms is discussed. |
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