July 26


Interview Question and Answer – AS400 Subfiles

By NickLitten

July 26, 2012

dusty, interview, questions, subfiles

Twenty years ago these are the kind of things you had to know to work on the old AS400 systems. I found these on an old dusty corner of my homeserver. Enjoy the trip down memory lane or to use old RPG lingo AS400NERD CABEQ ‘1’  START


What is a subfile ?

Subfile is a group of records of same record format and can be read from or write to the display in a single operation.

What are the contents of subfile ?

Subfile Record Format, Subfile Control Record Format, Relative Record Number, Subfile Record Number, Associated Subfile Keywords.

What are the two record formats that a subfile contains ?
Subfile record format(SFL), and subfile control record format(SFLCTL).

What is SFLPAG and SFLSIZ ?
SFLPAG : it is an attribute which specifies the number of records that can be displayed in a screen.
SFLSIZ : it is an attribute which specifies the number of records can be stored in the subfile.

What is the maximum number of subfiles that can specified in a display file ?

The maximum number of subfiles that can defined in a RPG program for one display file is ___ .

The maximum number of subfiles that can be active for a single file is____ .

What are the different opcodes used for file operation on a subfile in a RPG Program ?

Can more than one subfile record be displayed on one line ?
Yes, by using SFLLIN keyword.

How do you specify the number of records to roll in a subfile ?
Use SFLROLVAL keyword in DDS along with the number, which specifies the number of records to scroll at a time.

How will you display a particular page in subfile ?
Move a valid relative record number(RRN) in the field specified using SFLRCDNBR keyword in DDS.

How to pick up the changed records every time in a subfile after the first change made ?
Seton SFLNXTCHG keyword indicator and update the subfile record.

What is the use of the SFLEND keyword ?
By specifying this keyword, the Bottom/More message could be displayed at end of screen.

How do you toggle between single line and multi-line display of a particular record in a subfile ?
Using SFLDROP keyword.

Explain the difference between defining Subfile and Message-subfile ?
A subfile record is defined by SFL keyword, whereas a message subfile is defined by SFLMSG keyword.

Can a single screen format occupy a screen area above and below a subfile format ?
Not possible.

How can a program be prevented from failing over when READC is performed on an empty subfile ?
Check indicator placed in position LO, which will be seton if EOF if reached.

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