There's perhaps a less known tunning that allows for parallel updating of multiple zones.
The num_proc setting is at /etc/patch/pdo.conf and described at pdo.conf(4).
The recommendation is to have num_proc equal to the on-line CPUs.
Thus, on a system with 4 online CPUs:
# psrinfo
0 on-line since 10/18/2012 06:28:18
1 on-line since 10/18/2012 06:28:18
2 on-line since 10/18/2012 06:28:18
3 on-line since 10/18/2012 06:28:18
A setting of 4 is recommended:
# cp -p /etc/patch/pdo.conf{,.0}
# vim /etc/patch/pdo.conf
# grep num_proc= /etc/patch/pdo.conf
# num_proc=
# num_proc=1 # default entry
num_proc=4
