Wednesday, 28 January 2015

70 TOP VSAM Interview Questions and Answers

1. What are the different types of VSAM files available?
ESDS: Entry Sequence Data Set
KSDS: Key Sequence Data Set
RRDS: Relative Data Set

2. what is purpose of VSAM?
VSAM acts as an interface between Application program & Operating System.

3.What is the maximum record length for the VSAM dataset?
Max size of a record in VSAM is cylinder = 2880 bytes approx.

4.What is File Status in VSAM?
The File STATUS clause of the FILE-CONTROL paragraph allows for each file to be associated with afile status key (i.e., the 2-character data item specified in the FILE STATUS clause). If the FILE STATUS clause is specified for a given file, a value indicating the status of each I/O operation against that file is placed in the accociated file status key. This value is stored in the file statuskey as soon as the I/O operation is completed (and before execution of any EXCEPTION/ERROR declarative or INVALIDKEY/AT END phrase associated with the I/O request).
Note: This element may behave differently when the CMPR2 compiler option is used. The file statuskey is divided into two status keys: the first character is known as file status key1; the second character is file status key 2.

5. What is VSAM?
VSAM stands for Virtual Storage Access Method. It's a Data Management method used to organize, store, catalog, retrieve and delete the datasets in mainframe system (VSAM and Non-VSAM). This access method makes it easier for an application to execute an I/O operation (moving data between an I/O device and memory). In fact VSAM is the first access method designed for Virtual Storage Environment.
VSAM supports fixed as well as variable length records. These records are placed in blocks of Control Intervals and these control intervals are further placed as Control Area (CA consists of multiple CIs).

6. What are the advantages of VSAM?
Accessing the data is faster and easier.
VSAM supports more dataset types.
Supports variety of I/O Techniques.
Improves Efficiency.
Records can be accessed sequentially or randomly.

7. What are the disadvantages of VSAM?
VSAM Datasets require more storage space compared to other type of datasets due to Control information(CI) present in them.
VSAM can’t be stored in TAPE Volume i.e., VSAM Stored only in DASD.
VSAM is not a database like DB2, IMS DB & IDMS.
8. What is an alternate index and path?
An alternate index is an another way of accessing key sequenced data record stored in a base cluster and path is the linkage which connect alternate index to its base cluster.

9. Is a delete operation possible in an ESDS? B, is rewrite operation possible in ESDS?
No delete operation is not possible in VSAM ESDS.B. yes rewrite operation is possible in an ESDS.

10. What is the difference between LDS and ESDS?
There two datasets are VSAM datasets. ESDS maintains control information. But LDS does not maintains the control information.

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