never-committedTracked data was never explicitly flushed, so an interrupted attempt can lose everything since the start.
Progress survives a clean exit but vanishes after a crash, a dropped connection, or a laptop lid closing. The loss is all-or-nothing rather than partial.
A SCO set values but never called Commit (2004) or LMSCommit (1.2).
SetValue writes to the LMS's in-memory copy of the data model. Commit is the instruction to persist it. Many systems also persist on Terminate, which is why this often goes unnoticed until something interrupts an attempt — the one situation the call exists for.
Commit at meaningful checkpoints: the end of a page or module, after a question is answered, and before any long stretch of video. Do not commit on every SetValue; on a busy course that is a write storm, and some systems throttle or reject it.
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Stuck on this one, or seeing it only in a particular LMS? That is usually a short conversation — scormspecialist.co.uk.