what is the vas_ccache_renew process
The vas_ccache_renew process handles the tgt renewals (Kerberos Ticket Granting Ticket). When you log in you get a /tmp/krb5cc_<uid> ccache. If configured to be so, it can be renewable. By default the TGT inside it is good for 10 hours. But if you want it usable for longer then set it to renewable, and if you renew it before 10 hours is up, its good for another 10 hours.