BO4 - Cache clearing - impcat and best practice

Hi,

We are trying to get to bottom of a 30270 message and one of steps being asked to do by sap support is clear tomcat cache + webi proc server cache.

Have a couple of questions

1)  Are these not cleared automtically when SIA is stopped? - we have 2 nodes in cluster and stop the SIA each night on both nodes to do backup and to astop any possible contention of reports running while  ETL running.

2) What impcat would this have generally

3) Whilst will do druing downtime,  is this an activity we should regularly schedule or just something to do after a sp upgradee for example.

Any other thoughts/best practice on cache clearing generally.

Thanks

Philip