The Oracle docs are not really the reference documentation for the open-source stuff, since illumos and Oracle Solaris have diverged quite a bit by now. Some things are implemented in different ways. OpenZFS in illumos has many features not in the closed oracle zfs.
The real reference docs are the man pages [1].
Depending on the illumos distribution there are more task-oriented guides for OmniOS [2], OpenIndiana [3] or the SmartOS Wiki [4].
In-depth information (driver development, MDB, DTrace) is written down in the "illumos books" [5].
These are not in danger from oracle.
Sadly a lot of good historical documentation is already gone since oracle broke all the sun.com links and not even archive.org has those. :(
The real reference docs are the man pages [1]. Depending on the illumos distribution there are more task-oriented guides for OmniOS [2], OpenIndiana [3] or the SmartOS Wiki [4]. In-depth information (driver development, MDB, DTrace) is written down in the "illumos books" [5]. These are not in danger from oracle.
Sadly a lot of good historical documentation is already gone since oracle broke all the sun.com links and not even archive.org has those. :(
[1] https://illumos.org/man/
[2] https://omnios.omniti.com/wiki.php/GeneralAdministration
[3] http://docs.openindiana.org/handbook/getting-started/
[4] https://wiki.smartos.org/display/DOC/SmartOS+Users+Guide
[5] http://illumos.org/books/