IMS DB Tough Questions (2 of 3)

Interview questions on IMS DB asked mainly on search fields and DLI calls.

Read IMS DB interview questions-Part:1, if you miss it.

1) How many search fields are possible in a segment?

255 search fields are possible in a segment. Therefore 255 +1 (key)=256 search fields are possible

2) Why GNP call is required after GU call?

GNP call retrieves the occurrences of a subordinate segments under, which parentage was established

3) What is the size of DLI function?

Size of the DLI function is 4 bytes – X(4)

4) What is ‘*’ in SSA?

‘*’ 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) How to give multiple command codes?

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) What is “_” in command code?

‘-‘ Indicates it is NULL command code

7) What is ‘D’ command code?

‘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) What is ‘P’ in proc option?

‘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) What is ‘C’ command code?

“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) What are the main components in PCB?

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.