Material master locked is when one user will try to use material code which is currently used by another user so he will get the message that material is locked by user.
Blocked means we can't do any further processing action at the block level and using program run we can able to delete the material, using MARA, MARC MARD tables can find the different level of Blocking and Flag for deletions.(Tcode MM06)
Using T.code SE11--> MARA -->LVORM(X)
