After the system is installed, swap areas and swap files are listed in the /etc/vfstab file. They are activated by the /sbin/swapadd script when the system is booted.
An entry for a swap device in the /etc/vfstab file contains the following:
The full path name of the swap volume path name on a system with a ZFS root file system
File system type of the swap slice or swap file
The file system that contains a swap file must be mounted before the swap file is activated. So, in the /etc/vfstab file, ensure that the entry that mounts the file system comes before the entry that activates the swap file.