Most of Dynamics AX specialists (especially from support) heard about inventSumLogTTS table. Everyone knows that this table somehow is related to MRP; Everyone knows that if you do not run MRP, your inventSumLogTTS table grows bigger and bigger and eventually you need to clean it somehow. But since detailed documentation on static/dynamic plan update algorithms is absent, not many people understand how Axapta actually use this table for plan updates; what are advantages and caveats of dynamic vs static plan use;how order explosion differs from regeneration planning and so on…
I wrote this text mostly from my experience with Dynamics AX 2009. In the new version (DAX2012) approach remained the same from functional point of view, only technical details changed, so this information can be useful also for people using DAX2012.
A bit of history
As I wrote in my blog before, inventSumLogTTS table began its life (somewhere in late releases Axapta 2.5) only as a tool to track a list of changes which was applied to inventSum table in independent DB transaction. Should the main transaction be rolled back, the system was to iterate over related records in inventSumLogTTS and programmatically rollback changes to inventSum. Starting from Axapta 3.0, inventSumLogTTS table started to be also used to support dynamic update to MRP plan. In version Dynamics AX 4.0, the whole Inventory MultiTransaction System was dropped from Axapta and replaced with a new approach. Nevertheless inventSumLogTTS table still exists in the system, but nowadays it is used only to support dynamic MRP plan update. Today, name of the table is misleading, because now it is not used to log InventSum updates. As of versions 4-2012, it is used only to keep track of inventTrans changes, which have not been applied to dynamic plan yet.