An Improved Index Sequential Access Method Using Hashed Overflow The Index Sequential Access Method (ISAM) is one of the most important file management systems used with moveable head disk devices. This study investigates the use of an unconventional method of treating overflow records. The method is to use hashing techniques to allocate space for such records. If certain conditions are satisfied, this is superior to the conventional ISAM method of chaining the overflow records via linked list techniques. These conditions are: long overflow chains with significant overflow; lack of tight disk space constraints; record keys which are small compared to the total record size; and significant use of the file in the index as opposed to the sequential mode. Using hashed overflow, the time to locate a record is dependent not on the total volume of overflow records as in conventional ISAM, but on the percentage use of space dedicated to overflow records. CACM May, 1972 Mullin, J. K. ISAM, index sequential, hashing, scatter storage, disk, cylinder, overflow 3.72 3.73 3.74 CA720501 JB January 31, 1978 12:29 PM 1676 4 2359 1682 4 2359 1728 4 2359 1860 4 2359 1973 4 2359 2018 4 2359 2032 4 2359 2033 4 2359 2107 4 2359 2109 4 2359 2203 4 2359 2251 4 2359 2258 4 2359 2319 4 2359 2313 4 2359 2359 4 2359 2359 4 2359 2437 4 2359 2524 4 2359 2543 4 2359 2552 4 2359 2552 4 2359 2559 4 2359 2781 4 2359 2860 4 2359 2991 4 2359 2991 4 2359 3053 4 2359 1785 5 2359 2203 5 2359 2359 5 2359 2359 5 2359 2359 5 2359