Countermeasures against consistency anomalies in distributed integrated databases with relaxed ACID properties

In central databases the consistency of data is normally implemented by using the ACID (Atomicity, Consistency, Isolation and Durability) properties of a DBMS (Data Base Management System). This is not possible if distributed and/or mobile databases are involved and the availability of data also has to be optimized. Therefore, we will in this paper use so called relaxed ACID properties across different locations. A database is DBMS consistent if its data complies with the consistency rules of the DBMS´s metadata. If the database is DBMS consistent both when a transaction starts and when it has been committed and completed, the execution has the consistency property. The above definition of the consistency property is not useful in distributed databases with relaxed ACID properties because such a database is almost always inconsistent. In the following, we will use the concept Consistency anomalies for the inconsistencies caused by the missing consistency property in distributed integrated databases with relaxed ACID properties. In this paper, we will describe countermeasures against the consistency anomalies to make it possible to reduce or prevent the consequences of the missing distributed consistency property.