IMS/DB Interview Questions & Answers

Question 1. What Is A Hierarchy Path?

Answer :

Hierarchy path is a line that starts at the root, passes through the intermediate levels in the hierarchy, and ends at a segment at the bottom of the hierarchy.

Question 2. What Is A Root Segment?

Answer :

A segment that lies at the top of the hierarchy is called the root segment. It is the only segment through which all dependent segments are accessed.

Question 3. What Are Twin Segments?

Answer :

Two or more segment occurrences of a particular segment type under a single parent segment occurrence are called twin segments.

Question 4. Define Segment Occurrence?

Answer :

A segment occurrence is an individual segment of a particular type containing user data.

Question 5. What Is A Database Record?

Answer :

Each occurrence of the root segment plus all its subordinate segment occurrences make up for one database record.

Question 6. What Is The Limitation On The Number Of Levels In A Dl/i Database?

Answer :

We can have 15 levels in a DL/I database.

Question 7. How Many Segment Types Can You Have In A Dl/i Database?

Answer :

A DL/I database can have 255 segment types.

Question 8. What Are The Control Blocks In Ims?

Answer :

There are two control blocks: the Database Descriptor (DBD) and Program Specification Block (PSB).

Question 9. What Are Common Dli Functions?

Answer :

The common functions are GU, GN, GNP, GHU, GHN, REPL, ISRT, and DLET.

Question 10. What Are The Command Codes And Their Purposes?

Answer :

Command codes extend the function of an SSA call. They simplify programming and improve performance.

Question 11. What Is The Use Of Procopt?

Answer :

Procopt parameter specifies PROCESSING OPTIONS that define the type of processing performed on a segment.

Question 12. What Is Multi-positioning?

Answer :

Multi-positioning is an option whereby the IMS maintains a separate position on each hierarchical path. When more than one PCBs refer to the same DBD, it is called multi-positioning.

Question 13. Define A Search Field?

Answer :

The field that is used to retrieve the data is known as a search field.

Question 14. What Is A Goback Statement?

Answer :

A Goback statement is used to pass the control back to the IMS control program.

Question 15. Define A Call Statement?

Answer :

A Call statement is used to request for DL/I services such as performing certain operations on the IMS database.

Question 16. What Is The Function Of A Gu Call?

Answer :

'GU' or Get Unique works similar to the random read statement in COBOL. It is used to fetch a particular segment occurrence based on the field values which can be provided using Segment Search Arguments.

Question 17. What Is The Function Of A Ghu Call?

Answer :

'GHU' or Get Hold Unique specifies that we are going to update a segment after retrieval. GHU corresponds to the GU call.

Question 18. What Is The Function Of Ssa?

Answer :

SSA is known as Segment Search Arguments. SSA is an optional parameter. It is used to identify the segment occurrence being accessed. We can include any number of SSAs depending on the requirement.

Question 19. Explain Index Pointer Segment?

Answer :

DL/I stores the pointer to segments of the indexed database in a separate database. Index pointer segment is the only type of secondary index.

Question 20. Which Is The First Statement In Cobol-ims Programs?

Answer :

Entry statement is the first statement after the procedure division.

Question 21. What Is The Return Code You Get After A Successful Ims Call?

Answer :

We receive spaces after a successful call.

Question 22. What Is The Use Of Sparse Sequencing?

Answer :

We can remove some of the index source segments from the index using sparse sequencing with secondary index database. Sparse sequencing is used to improve the performance. When some occurrences of the index source segment are not used, we can remove that. Sparse sequencing is also known as Sparse Indexing.

Question 23. Explain Logical Relationship?

Answer :

A logical relationship is a path between two segments related logically and not physically. Usually a logical relationship is established between separate databases. But it is possible to have a relationship between the segments of one particular database.

Question 24. What Are Logical Twins?

Answer :

Logical twins are the occurrences of a logical child segment type that are subordinates to a single occurrence of the logical parent segment. DL/I makes the logical child segment appear like an actual physical child segment. This is also known as virtual logical child segment.

Question 25. What Is A Concatenated Segment?

Answer :

A logical child segment always begins with the complete concatenated key of the destination parent. This is known as Destination Parent Concatenated Key (DPCK). Always code the DPCK at the start of your segment I/O area for a logical child. In a logical database, the concatenated segment makes the connection between segments that are defined in different physical databases.

Question 26. Explain Dl/i Log?

Answer :

When an application program abnormally ends, it is necessary to revert the changes done by the application program, correct the errors, and re-execute it. To do this procedure, it is required to have the DL/I log.

Question 27. What Is A Checkpoint?

Answer :

A checkpoint is a stage where the modifications done to a database by an application program are considered complete and accurate.

Question 28. Which Database Processing Is Very Fast?

Answer :

IMS DB processing is very fast as compared to DB2.

Question 29. Which Database Is Difficult To Manage?

Answer :

IMS predefined tree structure reduces flexibility and it is difficult to manage.

Question 30. Through Which Segment All Dependent Segments Are Accessed?

Answer :

A segment that lies at the top of the hierarchy is called the root segment. It is the only segment through which all dependent segments are accessed.

Question 31. How Can We Access The Data In Ims Db?

Answer :

Data can be processed in both the ways: Sequential & Random.

Question 32. What Is The Predefined Pattern For Sequential Processing?

Answer :

Predefined pattern for accessing data in DL/I is first down the hierarchy, then left to right.

Question 33. For Field Macro Statement In Dbdgen, What Does Type=p Parameter Specifies?

Answer :

TYPE=P specifies Packed decimal data type for the field which we have declared.

Question 34. For Field Macro Statement In Dbdgen, What Does Type=x Parameter Specifies?

Answer :

TYPE=X specifies Hexadecimal data type for the field which we have declared.

Question 35. What Does Senseg Stands For?

Answer :

SENSEG is known as Segment Level Sensitivity. It defines the program's access to parts of the database and it is identified at the segment level.

Question 36. Which Parameter Specifies The Language In Which The Application Program Is Written In Psbgen?

Answer :

The LANG parameter specifies the language in which the application program is written, e.g., COBOL.

Question 37. Which Is Used To Pass The Control Back To The Ims Control Program?

Answer :

GOBACK is used to pass the control back to the IMS control program.

Question 38. Which Function Is Used To Get A Unique Record For Update Purpose?

Answer :

'GHU' code is used for Get Hold Unique. Hold function specifies that we are going to update the segment after retrieval. The Get Hold Unique function corresponds to the Get Unique call.

Question 39. Which Function Is Used To Retrieve Segment Occurrences In Sequence Subordinate To An Established Parent Segment?

Answer :

'GNP' code is used for Get Next within Parent. This function is used to retrieve segment occurrences in sequence subordinate to an established parent segment.

Question 40. Which Function Is Used For Recovering The Database?

Answer :

'CHKP' code is used for the Checkpoint function. It is used in the recovery features of IMS.

Question 41. In Pcb Which Field Is Used To Store The Level Of The Segment That Was Processed?

Answer :

Segment level is known as Segment Hierarchy Level Indicator. It contains character data and is two bytes long. A segment level field stores the level of the segment that was processed. When a segment is retrieved successfully, the level number of the retrieved segment is stored here.

Question 42. In Pcb Which Field Stores The Area For Its Own Internal Linkage Related To An Application Program?

Answer :

Reserved DL/I is known as the reserved area of the IMS. It stores four bytes binary data. IMS uses this area for its own internal linkage related to an application program.

Question 43. Which Ssa Provides The Name Of The Segment Being Used Inside The Call?

Answer :

An unqualified SSA provides the name of the segment being used inside the call.

Question 44. What Is The Length Of An Unqualified Ssa?

Answer :

A basic unqualified SSA is 9 bytes long. The first 8 bytes hold the segment name which is being used for processing. The last byte always contains space.

Question 45. Where Do We Code Command Code In A Qualified Ssa?

Answer :

Command code is coded at the tenth position.

Question 46. If A Call Is Successful What Value You Will Get In Status-code Field?

Answer :

If a call is successful you will get spaces in STATUS-CODE field.

Question 47. Multiple Pcbs Can Not Be Defined For A Single Database. State Whether True Or False?

Answer :

This statement is incorrect as Multiple PCBs can be defined for a single database.

Question 48. It Is Not Possible For A Program To Maintain Multiple Positions In A Database Using A Single Pcb. State Whether True Or False?

Answer :

This statement is incorrect as a program can maintain multiple positions in a database using a single PCB.

Question 49. For Bidirectional Virtual Relationship The Logical Connection Goes From The Logical Child To The Logical Parent And It Cannot Go The Other Way Around. State Whether True Or False?

Answer :

This statement is wrong as Bidirectional Virtual relationship allows access in both the directions. The logical child in its physical structure and the corresponding virtual logical child can be seen as paired segments.

Question 50. What Does Mpp Stands For?

Answer :

MPP stands for Message Processing Program.