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IMS Technical FAQ's


Q What is a DBD ?
A DBD stands for DATABASE DEFINITION. It is to define segements,key fields and access methods used for an IMS Database.
Q What is a PSB ?
A PSB stands for PROGRAM SPECIFICATION BLOCK.It is made up of one or more pcb's.It also defines the database used by the application program.
Q What is an ACB ?
A ACB stands for APLICATION CONTROL BLOCK.It Contains the information of the PSB with the corresponding DBD information.
Q What is SSA ?
A SSA stands for SEGMENT SEARCH ARGUMENTS which is used to describe which segments to be retrieved.
Q What are the different types of SSA's ?
A There are 2 types of SSA’S .
QUALIFIED SSA: It is used to retrieve a particular occurrence of a segment.
UNQUALIFIED SSA: It is used when no particular segment occurrence is requested.
Q What is the status code after a successful execuetion of a DL/I call ?
A The status code will have spaces after a successful execuetion of a a DL/1 call.
Q What are the four control blocks of Message Format Service (MFS) ?
A Message Input Data (MID):Describes the input message as the application program sees it.
Message Output Data (MOD):Describes the output message as the application program formats it.
Data Input Format (DIF):Describes the screen format for accepting input from the user.
Data Output Format (DOF):Describes the screen format as the user sees it.
Q What are the the 3 essential fields required for a DL/I call ?
A Function Code(GU,GHU,ISRT,REPL...)
PCB Mask
I/O Area

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