[OpenIndiana-discuss] what do pkg install phases mean?

[Richard L. Hamilton]

Given the output
----- output begins ------
root at openindiana:~# pkg update
            Packages to update: 375
       Create boot environment: Yes
Create backup boot environment:  No

DOWNLOAD                                PKGS         FILES    XFER (MB)   SPEED
Completed                            375/375     5209/5209  181.4/181.4  878k/s

PHASE                                          ITEMS
Removing old actions                       1015/1015
Installing new actions                     1017/1017
Updating modified actions                  6585/6585
Updating package state database                 Done 
Updating package cache                       375/375 
Updating image state                            Done 
Creating fast lookup database                   Done 
Updating package cache                           2/2 

A clone of openindiana-2023:03:03 exists and has been updated and activated.
On the next boot the Boot Environment openindiana-2023:03:05 will be
mounted on '/'.  Reboot when ready to switch to this updated BE.

Updating package cache                           2/2 

---------------------------------------------------------------------------
NOTE: Please review release notes posted at:

https://docs.openindiana.org/release-notes/latest-changes/
---------------------------------------------------------------------------

----- output ends -----

what do the various phases mean? And what drives the decision whether to create a new boot environment, or a backup boot environment (or maybe neither)?

Knowing those might be helpful if anything went badly wrong (although the simplest remedy would be to fall back to a previous boot environment!) or if one intended to create a package, and would certainly be more satisfying waiting for the slower phases to complete, being able to say to oneself what it was doing then.  Oh, and why does "Updating package cache" appear twice?

Updates on Solaris 11 and derivatives (OpenIndiana, etc) are certainly very robust (if packages and repositories are correct!) and provide generous means of recovery. But they do seem to be quite slow compared to e.g. either Red Hat based or Debian based Linux methods (yum or apt, or the underlying local-only facilities). That's not counting download time either (since repository servers are not all equal).