81.What are the disadvantages of using VARCHAR?

• Can lead to high space utilization if most of the values are close to maximum.
• Positioning of VARCHAR column has to be done carefully as it has performance implications.
• Relocation of rows to different pages can lead to more I/Os on retrieval.

82.How do I create a table MANAGER ( EMP#, MANAGER) where MANAGER is a foreign key which references to EMP# in the same table? Give the exact DDL.

First CREATE MANAGER table with EMP# as the primary key. Then ALTER it to define the foreign key.
When is the authorization check on DB2 objects done - at BIND time or run time?
At run time.

83.Define DB2.

DB2 is a Database Management System for the MVS Operating System where, DB2 is a subsystem of MVS Operating System.

84.What is the purpose of using COMMIT?

The data changes can be made permanent by using COMMIT. It also permits data to be accessed by other applications who can reference the committed data

85.List out the Data types available.

• SMALLINT
• INTEGER
• FLOAT
• DECIMAL
• CHAR
• VARCHAR
• DATE
• TIME

86.What are the uses of DB2 Optimizer?

• It processes SQL statements.
• It helps to select the access path

87.Define SQLCA.

SQL Communication Area is a structure of variables, which are updated after every execution of SQL statements. For an application that contains executable SQL statements, only one SQLCA is needed. FORTRAN need more than one SQLCA to be provided .For Java, SQLCA is not applicable.

88.Define CHECK constraint.

It is specified as a condition or criteria to ensure data integrity. A value to be inserted or updated to a table is tested by CHECK constraint. The CHECK constraints are created during the creation of the table.

89.What is SQLCA’s maximum length?

136 is the maximum length of the SQLCA.

90.Discuss about DB2 bind?

The process that builds access paths to the DB2 table is known as bind. The bind uses Database Request Modules from the DB2 pre-compile step as input and produces an application plan. It checks for user authentication and validates SQL statements in the DBRM(s).

91.List out the three types of page locks that can be held?

• Exclusive
• Update
• Share.

92.Define buffer pool.?

The buffer pool is a reserved main storage, which is to satisfy the buffering requirements for one or more table spaces or indexes. It can be made up of either 4K or 32K pages.

93.Explain the function of Data Manager?

The physical database is managed by the DB2 component called Data manager. It invokes other system components to perform logging, locking etc.

94.What is a storage group (STOGROUP)?

STOGROUP is a named collection of DASD volumes, which is to be used by index spaces and table spaces of the database.

95.Define predicate?

Predicate is an element of a search condition. It expresses or implies a search condition.

96.Define Declaration Generator (DCLGEN)?

Declaration Generator is a facility that is used to form SQL statements that describes a table or view. At pre-compile time, the table or view descriptions are then used to check the validity of SQL statements.

97.List out the buffer pools in DB2?

There are four buffer pools in DB2 and they are:

• BP0
• BP1
• BP2
• BP32

98.Define clustering index?

Clustering index is a type of index, which locates the table rows and determines how to group the rows together in the tablespace.

99.What is concurrency?

More than one DB2 application process can access the same data at the same time, is known as concurrency. However, problems can happen such as, lost updates access to unrepeatable reads and uncommitted data.

100.Explain the Function done by data manager?

Data manager can be considered as a component that is capable of managing the databases that are physically present and is capable of invoking other components associated with the system for performing functionalities like logging, locking and in performing other I/O operations.