Once drafted the initial commissioning schedule should be regularly reviewed.
If the first draft, or level 2 commissioning schedule was issued prior to your project reaching detailed design, there will be many changes to your plan. Detailed design means changes will probably occur, so the level 2 commissioning schedule needs to be constantly reviewed and updated to make it current with the project status at any one time. I would recommend at least a bi-weekly meeting with the commissioning planners to discuss changes to scope and dates, re-align links between systems and discuss the new issues that have arisen and get the plan re-formulated to put the commissioning plan back on track.
Do not also ignore the importance of sharing the commissioning plan with the construction group to reduce silo working and the aid the development of an overall aligned construction and commissioning schedule which is absolutely essential for an efficient and effective plant start-up.
Safe and successful commissioning to you always…