q1) if my intention for creating an ABE is just to use for patching / patchset update -
e.g. ./installpatchset -B secondboot --s10patchset
luactivate secondboot
What is the recommendation that my ABE should consist of ? and why ?
a) a separate device/slice for the / filesystem
b) a separate device/slice for / and swap
c) a separate device/slice for / , swap and /zones
q2) Does luactivate make changes the "boot-device" variable in OBP ?
Reason being I have a svm mirrordisk on /
md1 (PBE) - disk0, disk1
md2 (ABE) - disk2,disk3
boot-device - disk0, disk1
q3) if i luactivate ABE, what will my "boot-device" look likes ?
If you're using a ZFS boot, I've always liked creating new BEs in a different ZFS pool than the BE it's being copied from. If you put the new BE in the same ZFS pool, all that's done is making the new BE a clone of a ZFS snapshot. Over time, with each new BE made for patches/upgrades, the trail of snapshots and clones becomes unmanageable.
If you put the new BE in a different ZFS pool, the new BE is completely independent of the old one and a lot easier to manage.
That does mean you need two bootable ZFS pools, but I think it's worth it if you keep your servers up-to-date with a new BE every time a new patch set or upgrade is released.
Also make certain that users' home directories are not part of the boot environment. Users don't like having to use old copies of their home directories that were made when the BE was created.