| 摘要 |
PURPOSE:To reduce the record capacity of an index itself and at the same time to have a high-speed access to a desired record occurrence, by deciding the type of the index record occurrence in consideration of the key value of the record occurrence and the mutual relations among addresses having the record occurrence stored in the data base. CONSTITUTION:At the outset, the 1st index record type is defined with the record occurrence having the hundred million key value. Then the 2nd index record type is defined as long as the relation satisfies an equation I among relative code numbers of the record occurrence having the overlap key value. Here just a bit map item suffices if the displacement of N units of record relative numbers is within an (LBX8) range. Then plural bit map items are needed if said displacement exceeds the (LBX8) range. Otherwise the LB length can be increased. The 1st index record type is used in case the equation I is not satisfied despite the pressure of the overlap key value. As a result, the independent characteristics can be provided for each index to increase greatly the using efficiency of the index. |
