Dear Marianne
this is an "old" problem coming up very often. It is related to them "BOM" problem (BOMBOS interface is used here *** well often). Main issue: what is your definition of the "material" and that of "Real_sub".
Related to that to a certain extent is the topic of "batch" and assignment of batch classes to batches (to e.g. indicate the content of ingredients)
One option to deal with the situation is shown here:
Create REAL_SUB; attach e.g. one material
This material does have per plant a "different" BOM (= composition) (alternative BOM per plant; but could be as well produced in mnay plants but in different way).
Now you can try to take care that in using a different approach in "usage". You can use th validity area type "PLANT" to do so.
So you can/could maintain on one REAL_SUB many compositions and you know which composition is valid for which plant. There is only one "but". Normally you have or can have different BOMs in one plant per thee sam material (alternatives)
Here you could add a "note" in the data value assignment to reflect that or you could use a "user defined text". The main issue is: you have not "useful" selection criteria for many subsequent processes. Only by using the "note" you could may be differentiate
E.g. if you have two BOMs per material (alternative BOMs) with "different" compostion in the same plant the result would be:
Sort Seq 1: Usage: STANDARD / 0001 (0001 should be the code for the plant)
Sort Seq 2: Usage: STANDARD / 0001 (0001 should be the code for the plant)
So the usage is the same.
But may be I did not completely understood your scenario correct
Regarding REACH I can provide only suggestions: don't do it like you seem to have implemented it. You will get trouble in SVT, DG...... and many other EH&S processes; not talking about the trouble in SAP SD, PP, MM, QM, BW .... etc. etc. (check please: configurable material as search criteria as well; the same: recipe etc.)
Second option
E.g. let us assume this: you would like to drink a cup of coffee. Sometimes you add two pieces of sugar, three or one; someties you add more milk, some times less milk. At the end you "as the consumer" is completely satisfied with your cup of coffee.
In terms of EH&S: we have three "ingredients"; Coffee, sugar, milk but in "mixed" proportions. What you can do is to maintain like this in composition (high level example; only to give you the idea)
Min Max Ave value
Milk 1 ml 3 ml 2 ml
Sugar 1 piece 3 piece 2 piece
Coffee 40 ml 60 ml 50 ml
In doing so normally you satisfy any product safety, dangerous goods etc. needs including MSDS generation etc. etc. This is the most common used approach to deal with your situation (if I understand your situation correct). REACh demands can be fulfilled the same
C.B.
PS: normally such discussions as yours are coming up due to SAP EHS SVT installation (or as in your case because of REACh SDS); here you will get trouble as well if you would like to track something with SAP EHS SVT.
Reach SDS/MSDS: here you should have "less" stress as you in case of a mixture normally you need only to take care chapter 2, 3, 8; but not taking care about appendix; in case you afre mixing (as in my coffee example) you will have less problem in SVT; in case of reaction: you will have problems
Proposal: before you go on: make an analysis; how often is the problem coming up in your company; if we are talking about < 1000 materials: keep your solution simple; if the problem comes up to often you need to figure out which approach might be the right one starting with "As is" situation and defininig new "to be" one. Regarding Reach in general: you are to late if we talk in IT topis; this year (this month !) your company must ! register the next wave of substances which are Reach relevant; then 2018 we (than means chemical companies) need to deal with the last wave; this is a further reason to use a very simple solution to fulfill Reach needs.