Run Onyx before update, run all the maintenance tasks.
Updating the same drive you are booted from adds more risk. If you have two bootable partitions A and B, boot to A to update B, boot to B to update A. If possible, boot from another partition than the one you are updating. I always recommend the Combo, even if you are just upgrading from the previous version. 10.11.5 combo update (updates any version of 10.11.x)
