IMS DB Interview Preparation Guide Download PDF
IBM Information Management System (IMS) is a joint hierarchical database and information management system with extensive transaction processing capabilities.
39 IMS DB Questions and Answers:
Table of Contents:
1 :: What are the path calls in imsdb?
Path call retrieve all the segment occurrence present for an particular DB or root segment
2 :: Portfolio analysis application is an example of?
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3 :: What is the maximum of key fields and search fields allowed in a segment?
Key fields - Only 1
Search fields - No limitation
Search fields - No limitation
4 :: What is the maximum number of PCBs allowed in a PSB?
Any number more than 1 (no limitation)
5 :: What are the two ways in which DL/I interface can be invoked?
► By making a call to IBM supplied program CBLTDLI / ASMTDLI / PLITDLI
(most commonly used method) by - Passing a PCB, or Passing an AIB
► By invoking the EXEC-DLI CICS interface by Passing a PCB, or Passing an AIB
(most commonly used method) by - Passing a PCB, or Passing an AIB
► By invoking the EXEC-DLI CICS interface by Passing a PCB, or Passing an AIB
7 :: What is the maximum number of fields allowed per segment and what is the maximum number of fields per database?
Max. number of fields per segment = 255
Max. number of fields per database = 1000
Max. number of fields per database = 1000
10 :: What are the retrieval sequences in IMS DB?
► Top to Bottom
► Front to Back
► Left to Right
► Front to Back
► Left to Right
11 :: Can we use PROCOPT on PCB and Segment field (SENSEG)?
Yes, we can use the PROCOPT on PCB macro (at database level) or sensitive segment macro (at segment level).
12 :: What is meant by BMP mode?
It is of two types:
Transaction oriented
► Can read and write to online message queues.
► Can process online files and databases.
Batch oriented
► Can only read message queues.
► Access online databases in Batch mode
Transaction oriented
► Can read and write to online message queues.
► Can process online files and databases.
Batch oriented
► Can only read message queues.
► Access online databases in Batch mode
13 :: What is meant by MPP mode?
► True Online processing.
► Transaction are entered at terminal and stored in message queue.
► Databases accessed must be offline.
► Transaction are entered at terminal and stored in message queue.
► Databases accessed must be offline.
14 :: What is meant by Batch DL/I mode?
► True Batch processing.
► No data communication services are used.
► Databases accessed must be offline.
► No data communication services are used.
► Databases accessed must be offline.
15 :: What are the processing modes available in IMS DB?
► Batch DL/I
► MPP Mode - (Message Processing Program)
► BMP Mode - (Batch Message Processing)
► MPP Mode - (Message Processing Program)
► BMP Mode - (Batch Message Processing)
16 :: What is the advantage of creating the ACBs well ahead of time?
► Application program's scheduling consumes less time
► Less storage
► Less storage
17 :: What is the disadvantage of dynamic generation of ACB?
Everytime the program is run., the ACB needs to be built.
18 :: What is the advantage of dynamic generation of ACB?
It can be made sure that the ACB generated incorporates all the latest changes to the PSB and DBD.
19 :: Explain ACBGEN process?
ACB is a consolidation of PSB and DBD information.
► For online programs
ACBs must be prebuilt using the ACBGEN utility i.e., ACBGEN must be run which will merge DBD and PSB and generate ACB.
► For batch programs
ACBs can be generated either at execution time (dynamically using IMS.DBDLIB and IMS.PSBLIB as input (PARM=DL/I)) or ahead of time (prebuilt ACB from IMS.ACBLIB can be used (PARM=DBB)).
► For online programs
ACBs must be prebuilt using the ACBGEN utility i.e., ACBGEN must be run which will merge DBD and PSB and generate ACB.
► For batch programs
ACBs can be generated either at execution time (dynamically using IMS.DBDLIB and IMS.PSBLIB as input (PARM=DL/I)) or ahead of time (prebuilt ACB from IMS.ACBLIB can be used (PARM=DBB)).
20 :: Explain PSBGEN process?
PSBGEN control statements consists of Assembler Language macro statements. The macros are supplied by IBM in a library named IMSVS.MACLIB. That invokes a cataloged procedure usually called PSBGEN and stored in PSBLIB. Each PSB consists of one or more control blocks called Program Control Block (PCB). Each PCB within a PSB defines one logical structure. All the PCBs within a PSB are collectively knows as an Application Data Structure.
IMS allows a PSB to define more than one logical data structure because a program is allowed to access to more than one database. A program us also allowed to concurrently access different parts of the same database. IMS allows the DBA to define any number of logical data structure in a single PSB.
IMS allows a PSB to define more than one logical data structure because a program is allowed to access to more than one database. A program us also allowed to concurrently access different parts of the same database. IMS allows the DBA to define any number of logical data structure in a single PSB.
21 :: What information does a PSB contain?
PSB information includes:
► PCB - defines the database to be accessed by the application program.
► SENSEG - defines the segment types to which the application program will be sensitive.
► SENFLD - defines the fields in the segment type to which the application program will be sensitive.
► PROCOPT - defines the types of access to the database or segment.
► PCB - defines the database to be accessed by the application program.
► SENSEG - defines the segment types to which the application program will be sensitive.
► SENFLD - defines the fields in the segment type to which the application program will be sensitive.
► PROCOPT - defines the types of access to the database or segment.
22 :: What are the two types of fields available in IMS DB?
Key Fields - (PROCOPT=K)
► Used to sequence the database and can't be changed
► It’s the field within a segment, used to identify the occurrence of the segment
► used to maintain the IMS segments in ascending sequence.
Search Fields - (PROCOPT=G)
► Used to search for a segment, without the segment being sequenced on that field
► A segment need not have a key or search field.
Both types of fields can be used to search the database.
► Used to sequence the database and can't be changed
► It’s the field within a segment, used to identify the occurrence of the segment
► used to maintain the IMS segments in ascending sequence.
Search Fields - (PROCOPT=G)
► Used to search for a segment, without the segment being sequenced on that field
► A segment need not have a key or search field.
Both types of fields can be used to search the database.
23 :: What is a segment in IMS?
Segment is the smallest unit of information that IMS transfers to and from database. Segment may contain one or more fields.
24 :: Which languages does IMS support / application program languages?
COBOL, PL/1, C, VS Pascal, REXX, Ada and Assembler.
25 :: Explain DBDGEN process?
DBDGEN control statements consists of Assembler Language macro statements. The macros are supplied by IBM in a library named IMSVS.MACLIB. DBDGEN control statements are normally coded by the DBA and submitted to the system with JCL. That invokes a cataloged procedure usually called DBDGEN. The DBDGEN procedure causes the DBDGEN control statements to the processed by the assembler producing the object module. The object module is then passed to the linkage editor which, in turn, stores a load module in another IMS Library called as IMS.DBDLIB or IMSVS.DBDLIB.
The DBD process is normally preformed only once for a database. All applications use the DBD in accessing the information on the database. A new DBD is normally created only if the physical nature of the database changes.
The DBD process is normally preformed only once for a database. All applications use the DBD in accessing the information on the database. A new DBD is normally created only if the physical nature of the database changes.