Locking the position of a lesson

Locking a lesson means locking its position in the timetable. The lesson is still taken into account by the solver, but the automatic generation can no longer move it.

The visual cue to look for is a closed padlock . Conversely, an open padlock indicates that the position can still be moved by a generation or a reorganization operation.

Not to be confused: the placement icon is used to place a lesson on the timetable. It opens or activates placement; it is not the lock marker.

When to lock a lesson

Typical cases:

• External instructor whose schedule is imposed.
• Dated exam whose time slot or room is already settled.
• School trip or visit scheduled on a very specific time slot.
• External room with imposed hours (gym, swimming pool…): possible through locking, but it is often better to use the room's time constraints, which guide the solver without freezing each lesson one by one.
• Lesson of a free group placed manually next to a main lesson.
• Position obtained by a previous generation that you want to keep before running a broader generation.

How to lock

1. Place the lesson on the timetable if it is not there yet.
2. Open the lesson's position details.
3. Enable the closed padlock to lock the position.
4. Check that the lesson shows a padlock on its position.

To release the position, use the open padlock. The lesson can then be moved by a generation or by some reorganization operations.

Mass actions

In the hours distribution, the Actions menu also offers global operations:

• Lock all scheduled lessons locks the lessons already placed;
• Unlock all scheduled lessons removes the lock without removing the position;
• Cancel all scheduled lessons removes the lock and removes the position.

This last option is useful before a clean new generation, when you want to start over from unplaced lessons.

Effects on generation and the diagnostic

A locked lesson remains a strong constraint for the solver. The other lessons must fit around it.

An important consequence: if you lock a lesson on a highly constrained time slot, Omniscol respects that decision. Conflicts or warnings remain visible, but the lock indicates that the position is intentional. In the diagnostic, a problem carried by a locked lesson is therefore downgraded from a blocking alert (red) to a warning (orange): Omniscol reports the issue without imposing it as a blocker to fix.

Not to be confused

• Locking a lesson's position: the lesson keeps its time slot during the generation.
• Collaborative lock: a mechanism related to simultaneous editing by several administrators. See Real-time collaboration.
• Position locked with no room: a special case where a lesson must remain without an automatically assigned room, via Lock.

Good practice

• Before running a new generation, review the locked lessons: too many fixed positions reduce the room for optimization.
• After a testing phase, unlock whatever should not be kept.
• For free groups, place the lesson manually and then lock its position. See Free groups.