Hi, I would like to work with indecomposable representations over a commutative ring and start with $R=\mathbb{Z}_p$

Notations: $G$ a finite group, $S$ a subgroup, $R=\mathbb{Z}_p$ the p-adic ring, and $W$ an indecomposable $R[S]$ module

The Mackey criterion tells if an induced representation is

**simple**or not. How can one decide if it is**indecomposable**? I know just theorems which tell " If ... then $\operatorname{Ind}_S^G(W)$ is indecomposable". Is there something for the other direction to have "$\operatorname{Ind}(W)$ is indecomposable if and only if" ?Let $V$ be some finite generate $\mathbb{Z}_p[G]$ module. Is the decomposition of $V$ into indecomposables unique? I know that usually it would be necessary that the ring is artinian.

Thanks

edit: Is there maybe a theorem, which tells when an indecomposable representation from a normal subgroup extends to the whole group when working over $R$?