Google 4 Manual Book page 210

WARNING: Encryption is irreversible.
The only way to revert is to perform
a factory data reset, which erases all
your data.
Encryption provides additional protection
in case your phone is stolen, and may be
required or recommended in some organi­
zations. Consult your system administrator
before turning it on. In many cases the PIN or
password you set for encryption is controlled
by the system administrator.
Before turning on encryption, prepare as
follows:
1. Set a lock screen PIN or password.
2. Charge the battery.
3. Plug in your phone.
4. Schedule an hour or more for the encryp­
tion process: you must not interrupt it or
you will lose some or all of your data.
SECURITY SETTINGS 201