Split Mirror Backup DB2 v9 and Logging

Is there any specific logging requirements relating to a recoverable split mirror Backup on DB2 v9 ?

It does a write suspend but does that imagine need the active logs ( log_dir ) or archived logs to make it consistent ?

So Fundamentally is it valid to do a split mirror backup with logretain and userexit set to 'no'.

Thanks.

Regards Russell