This will take care of all planning file entries for all the materials created afterwards and that are relevant for planning.
 
If some materials are created before the activation of MRP, in that case we use this transaction MDAB, for those material to be entered in the planning file.
 
MDAB is for creating the planning file entries in background. So when you go-live you can schedule this job and it will create planning file entries for all the material in that plant. 
 
If required you can also schedule this job to be run once in a month to take care of all the new materials. (if you create them by batch jobs).  Also you can use this transaction along with consistency check for the planning file MDRE
 
 
1. What do MDAB does?
 
This creates a Planning file entry
 
2. Why do we run this for first time when MRP is started?
 
As the system needs to identity what all the materials that has to be included in the planning run.  
This Transaction creates a planning file entry to make the mrp run at background to pick the materials and to include in the MRP run.
 
3. Do we need to run regularly?
 
The answer is No.

Once the mrp is run the planning file entry will be removed and again it will be populated when a stock change occurs, a sales order gets created, etc.
 
 
Can we get a list of materials for those planning file entry is generated through background job using t-code MDAB ?
 
You will get that list from accessing database table MDVM or DBVM
 
 
Notes:
 
Planning File creates all the materials relevant for the planning run.
 
The planning run and the scope of the planning run (which materials are planned in which planning run) are controlled by the planning file.
 
For planning file entry use the following transactions,
 
MD20 : Create planning file entry
MD21 : Display planning file entry
MDAB : Set up planning file entry in background
MDRE : Check planning file entry Please run this in it will solve your problem
 
All materials assigned with MRP are automatically entered in planning file entry.
 
Depends on changes in material planning or in proposal, system will create planning file entry.
 
When MRP run, system will consider only which materials having entry in above contents of planning file entry. After MRP run, system delete the planning file entry. And again, when material have changes like GI GR on any other demand, then system generate planning file entry again.

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