MAIN STORAGE RESIDING SYSTEM FOR INDEX

PURPOSE:To improve retrieval efficiency by permitting all indexes in an access route during data retrieval to reside in a main storage. CONSTITUTION:On receiving a data readout request, a control facility ACC accesses a control table TBL by using an index control block YXCB and, when an index IX0 resides in a resident pool RB, refers to a block YXCB and a page control table PCT to find a buffer BUFF where the index is to be read, thereby reading the index IX0 to two. Then, the control facility ACC searches the control table TBL again and, if an index IX1 to be accessed next is not in the pool RB, attains direct access DASD by using a data control block DCB to read the index IX1 in the buffer BUFF, thereby storing the index IX1 in the pool RB. Then, an index IX3 to be accessed next is stored in the pool RB similarly.