Question { CitiGroup, 12815 }

How are datasets concatenated?

Answer

Datasets are concatenated by writing a normal DD statement for the first dataset and then adding a DD statement without a DDNAME for each dataset to be concatenated in the order they are to be read.

Example:
//STEP1 EXEC PGM=PGM1
//DD1 DD DSN=TSTA.CHAN.PS1,DISP=SHR
// DD DSN= TSTA.CHAN.PS2,DISP=SHR
// DD DSN= TSTA.CHAN.PS3,DISP=SHR

https://youtu.be/VE6cTuFpsXc
https://youtu.be/bExB_Tjp9A4
https://youtu.be/_O6gPk6jjLE

Question { IBM, 1163 }

what are the different types of vsam files available? Explain them

Answer

1. Entry sequential data set(ESDS) works like sequential file which contains only cluster and data components.
We must mention NONINDEXED while defining ESDS cluster.
It supports only sequential access in batch program.

2. Key sequential data set(KSDS) has three components(CLUSTER, DATA and INDEX).
We must code INDEXED while defining the KSDS cluster.
Data component consists of sorted records which are based on key values.
Index component consists of key values and the pointer to the data records.

3. Relative Record Data Set(RRDS) records are identified using Relative Record Number (RRN). Records are stored in numbered.

4. The linear dataset(LDS) is a byte-stream dataset which is commonly used in DB2 system. This dataset is rarely used in application programs.
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