O'Reilly logo
  • Chris Kang thinks this is interesting:

This initial phase, when the script is prepared but the rollback protection hasn't started yet, is called the Execute sequence's immediate phase.

From

Cover of WiX 3.6: A Developer's Guide to Windows Installer XML

Note

This is just before InstallInitialize phase, which marks the beginning of the point where rollback is supported, and when changes to the system actually starts.