The following material is a good starting point on Fujitsu Sequential file processing:

Always a good idea to look at the Getting Started Guide - Contains list of all samples.

Start by reading the help - NetCOBOL Users Guide.      Chapter 7 - File Processing.
                                                       Appendix B IO Status List.
Next Read the help in     - NetCOBOL Language Reference - Chapter 4 Environment Division
                                                          Chapter 5 Data Division
                                                          Chapter 6 Procedure Division

You can get to the information above by going to:

START --> Programs --> Fujitsu COBOL V10 --> Online Documentation
                          OR 
C:\Program Files\Fujitsu NetCOBOL for Windows\Manual\Manual.PDF

Sample programs to work with after reading the above information:

C:\Program Files\Fujitsu NetCOBOL for Windows\samples\cobol\Sample2 
(Sequential to Indexed.)
C:\Program Files\Fujitsu NetCOBOL for Windows\samples\cobol\Sample7 
(Indexed)


The maximum file size currently supported is 1Gig, unless you are on Red Hat
Linux Server, where it can be upwards of a terabyte.  Some other solutions
exist beyond 1G.


** The top challenges reported - and their solutions: **
Alternate index descriptions are different under FUJITSU.

YOu can name your alternate index, and reference the fields.
Under Fujitsu, you simply reference the fields in your SELECT, and don't
name the index.