If you do want to execute the code on OnModify trigger when you modify a record then you can use MODIFY(TRUE). If you don't want those code to be executed then you can use MODIFY. So which one to use is all up to you or depends on your requirement.
Software Developer,
Archerpoint India Pvt. Ltd,Chennai.
Answers
If you write SalesHeader.MODIFY(TRUE) - This will call the MODIFY trigger of Sales Header whereas SalesHeader.MODIFY will not.
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Archerpoint India Pvt. Ltd,Chennai.