An access method is:

The portion of a computer’s operating system responsible for formatting data sets and their direction to specific storage devices. Examples from the mainframe world include Virtual Storage Access Method (VSAM) and Indexed Sequential Access Method (ISAM).

In local-area networks, the technique or program code used to arbitrate the use of the communications medium by granting access selectively to individual stations. Examples are Carrier Sense Multiple Access with Collision Detection (CSMA-CD) and token passing.