The first boot of a system after update to Oracle Solaris 11.4 can experience delays as the system relocates portions of the data stored under /var into shared datasets under /var/share. Shared datasets are datasets that are not part of the Oracle Solaris 11.4 boot environment (BE) but are shared with all BEs. In some cases, such as when /var/tmp contains a very large amount of data, this data migration can fail to complete.
To avoid a large boot delay and incomplete data migration, before updating to Oracle Solaris 11.4, remove files stored in /var/tmp. Move any data that you want to keep into ZFS datasets that are outside the BE, for example under /export. Any data that remains in /var/tmp should be only data that cannot easily be moved, for example because that data is currently in use. Best practice is to not use /var/tmp for permanent data storage.
After booting into Oracle Solaris 11.4, inspect the SMF service log of the system/filesystem/minimal service for errors:
$ svcs -Lv system/filesystem/minimal
If any errors were logged while booting Oracle Solaris 11.4, reboot the system to attempt to complete the migration. Re-inspect the service log after reboot.