Review of query execution in DBMS H2

Research of query execution engines was carried out depending on the changes of query parameters. The relational DBMS H2 Database was investigated. Oracle Corporation’s freeware was used to realize virtualization of hardware environment. We have created experimental database consisting of many tables that have the same structure and different number of rows. In the course of the main experiment measurements of the query execution time depending on the relative row number in tables and values of the main memory were made. We decided on the use of the inverse function for approximation of measurement data. A significant decrease of the query execution time after first query execution was observed. A step like decrease of the query execution time under the increase of the main memory size was also noted. To determine the influence of cache value on the DBMS performance we have conducted an additional experiment. For certain queries with fixed values of main memories the cache memory was varied from to further values with 512 Kb. A sharp decrease in the query execution time (up to 25 times) was registered in the case of cache memory increase. This observation testifies to the fact that the only memory used during query execution was the main memory. Considering strong marked dependence of the H2 Database performance from cache technology, the raise of the value of data in the main memory it is possible to reduce the query execution time qualitatively.