Question

IBM's indexed sequential access method (ISAM)

a. uses an index file for sequential access
b. uses a small master index (kept in memory) that points to disk blocks of a secondary index, while the secondary index blocks point to the actual file blocks
c. use the pointers (kept in memory) of the actual file blocks
d. uses the pointers (kept in memory) that points to disk blocks of a master index which points to disk blocks of a secondary index, while the secondary index blocks point to the actual file blocks

a. 1
b. 2
c. 3
d. 4

Answer 1

The indexed sequential access method (ISAM) used by IBM involves a small master index that points to disk blocks of a secondary index, while the secondary index blocks point to the actual file blocks. This is the correct answer, which is option b. 2.

Step-by-step explanation:

IBM's indexed sequential access method (ISAM) uses a small master index (kept in memory) that points to disk blocks of a secondary index, while the secondary index blocks point to the actual file blocks. This is the correct answer, which is option b. 2. ISAM is a data access method used in computerized databases that allows for both random and sequential access to records.

IBM's Indexed Sequential Access Method (ISAM) uses a multi-level index structure with a small master index in memory pointing to disk blocks of a secondary index, which in turn points to actual file blocks on disk.

IBM's Indexed Sequential Access Method (ISAM) uses an index structure to facilitate both sequential and direct access to records within a file. The correct answer to how ISAM operates is option b: ISAM uses a small master index (kept in memory) that points to disk blocks of a secondary index, while the secondary index blocks point to the actual file blocks.

This means that ISAM utilizes a two-level indexing system where the upper level is the master index and the lower level is the secondary index. The master index is small enough to be kept in memory for quick lookups, which then directs the system to the correct block in the secondary index. The secondary index contains pointers to the actual data blocks on the disk where records are stored.