Friday, February 14, 2020



READC and SFLNXTCHG are the two popular keywords used when working with subfiles. This short post explains what is the use of these two keywords. 


READC is used to Read the Changed Records in a Subfile.


SFLNXTCHG is used to mark the Records in a Subfile as Changed.

SFLNXTCHG plays a Major role when there is a Subfile with Update capabilities.

While processing the Subfile, Changed Records can be read using 'READC'. However, In most cases where Update is involved it is essential to validate the data before Update.

Modified tag would be automatically turned off on a record when Program reads the Changed Record (using READC) for validation and wouldn't be able to read the record again for the actual UPDATE operation.

This can be controlled using SFLNXTCHG Keyword.

SFLNXTCHG can be used in two different ways.

  1. Use SFLNXTCHG Keyword without any indicator
  2. Control SFLNXTCHG Keyword with indicator. 

Using SFLNXTCHG without any indicator would mark all the records written into Subfile as Changed by default. And, all of these records can be read by READC even if there is no Change has been done by the Screen User.

This may take more time in processing the subfile and may not be required to read all the records specially when there are large number of records in Subfile.

Controlling SFLNXTCHG Keyword with indicator would be preferred in these cases.

When a record is changed, Record would be marked as 'Changed' by default and can be read using READC. Turn ON the Indicator on SFLNXTCHG Keyword once the record is read using READC and UPDATE the Subfile. This would mark the record as 'Changed' and can be read again using READC. 

Thursday, February 6, 2020

Session or Device Error Occured

Session or Device Error Occured

There are few scenarios where Subfile would crash with 'Session or Device Error Occured'.

Below mentioned are the few scenarios when this issue would occur.

  • Incorrect Record Number in SFLRCDNBR

Variable associated with Keyword SFLRCDNBR (RRN) should be greater than Zero

  • Displaying Empty Subfile

No Records to display and still SFLDSP indicator is ON.

  • Attempting to write more than 9999 records into Load All Subfile

Maximum number of records allowed on Load All Subfile is 9999. Attempting to write more than 999 would result in Program crash.

Different Ways of Sorting Data in a List - Python

Sorting Data in a List List is a collection of data (of different data types), much like an array. Like any data structure or data set, dat...