1) 255 search fields are possible in a segment. Therefore 255 +1 (key)=256 search fields are possible
2) GNP call retrieves the occurrences of a subordinate segments under, which parentage was established
3) Size of the DLI function is 4 bytes – X(4)
4) ‘*’ in the SSA states that Command code is followed.
Xxxxxxxx*C’ ‘ Here, xxxxxxxx Segment name
C- Command code
Space after command code states that end of SSA
5) Multiple command codes are possible. It is very rarely used.
Xxxxxxxx*CD’ ‘ C, D are command codes
Spaces states that end of command code
6) ‘-‘ Indicates it is NULL command code
7) ‘D’ Command code. If we want to retrieve the data of all segments, we need to give “D” command code in all the segments till the lowest level segment. This avoids giving of individual calls.So that performance can be improved.
8) ‘P’ Is the Proc option. We need to specify it in the PSB on the segment, where we give Path call. Else we get ‘AM’ status code
9) “C” concatenated command code. If we are interested on lowest level segment, we can give ‘C’ command code in the SSA of lowest level segment
10) The main components of PCB are Database name, Segment Level, Proc options, Segment name feedback, Key length feedback, Number of sensitive segments, Key feedback area.