DL/I calls against an HSAM database
Initial entry to an HSAM database is through GU or GN calls. When the first call is issued, the search for the desired segment starts at the beginning of the database and passes sequentially through all segments stored in the database until the desired segment is reached.
After the desired segment is reached, its position is used as the starting position for any additional calls that process the database in a forward direction.
After position in an HSAM database has been established, the way in which GU calls are handled depends on whether a sequence field is defined for the root segment and what processing options are in effect. The following figure shows a flow chart of the actions taken based on whether a sequence field is defined and what processing options are in effect.
