What is the difference between primary key & unique index ? 

TYPERUN=SCAN on the JOB card or use JSCAN.

TYPERUN=HOLD on the job card.

it is used for syntatical checks and direct job to spool and hold it.

An in-stream PROC is defined right in the jcl stream and doesn't reside in the proclib. This is an older technique associated with punched cards but it is still in use with setup and installation programs from vendors.

for the in-line perform instead of:

perform add-paragraph until switch = 'y'

you can code

perform until switch = 'y'

body of code

end-perform

body of code is the code from add-paragraph appearing in-line (ie right in the perform) instead of in a separate paragraph (out of line code)

Return Code in JCL can b obtained by the use of COND paramater...it is used to know the return codes of previous steps.

All indicate dataset out of space. SD37 - no secondary allocation was specified. SB37 - end of vol. and no further volumes specified. SE37 - Max. of 16 extents already allocated.

SYSPRINT: All system output will appear under this DD card. Suppose you are copying a VSAM file using IDCAMS. Then, number of records processed, highest condition code etc.. will appear under sysprint. You cannot customise SYSPRINT output.

SYSIN: This is nothing but SYStem INstruction. Suppose, you want to sort a file on certain key. You have to have following command under SYSIN.

SORT FIELDS = (starting-col,length,data-type,A/D)

SUM FIELDS = NONE

DUMMY: Mainly used where user is intended to simulate a program without creating an output file.

Batch DL/I

MPP Mode - (Message Processing Program)

BMP Mode - (Batch Message Processing)

Key Fields - (PROCOPT=K)

- Used to sequence the database and can't be changed

- It is 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.

A Field that DL/I uses to maintain the segments in the ascending order is called the key field