IMS DB Interview Questions Answers

1/17/2010 No Comment

Mainframe IMS DB Interview Questions. for Beginner Level Intermediate Advanced Level.

This questions can be expected in a Mainframe Interview.

What is PCB?
Answer : Program Communication Block defines which database the program will access and the type of access allowed. It is defines the programmer's view of the database.

What information does a DBD contain?

Answer : DBD information includes: 
  • Database name, Access method 
  • Dataset name 
  • Segment name, length, parent
  • Key field name, length, location, type
  • Search field name, length, location, type
Explain DBDGEN process?
Answer : 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.

Which languages does IMS support / application program languages?

Answer : COBOL, PL/1, C, VS Pascal, REXX, Ada and Assembler.

What is a segment?

Answer : Segment is the smallest unit of information that IMS transfers to and from database. Segment may contain one or more fields.

What are the two types of fields available in IMS DB?

Answer : 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.
What information does a PSB contain?
Answer : 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.
Explain PSBGEN process?
Answer : 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.

What is the advantage of IMS over DB2?

Answer : IMS is much faster than DB2, despite the improvements in DB2 since the mid 80's, and is still used heavily for high-speed transaction processing - airlines, banks, and tracking systems. The number of IMS installations throughout the world is still increasing.
Related Posts


No comments :

 

Aired | The content is copyrighted and may not be reproduced on other websites. | Copyright © 2009-2016 | All Rights Reserved 2016

Contact Us | About Us | Privacy Policy and Disclaimer