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Shared Lock - Multiple users can access data in display mode. New change mode requests will be rejected is an object is SHARED LOCK
Exclusive Locks - Restrict other users to put any kind of lock on the same object
Exclusive but not cumulative lock - It is same as Exclusive lock except the fact that even the lock requests from the same transaction will also be rejected
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"If reusability is not the concern then we can go ahead with Open SQL only.
If reusability is needed then CDS is very useful also it can further be used in Odata & Fiori.
AMDP is useful when we want to have some very complex logic which requires looping and all also the need is to use SQL Script then we can go ahead with AMDP. But now with the birth of CDS table function we can use AMDP inside CDS."