Initially, swap space is allocated as part of the Solaris installation process. If you use the installation program's automatic layout of disk slices and do not manually change the size of the swap slice, the Solaris installation program allocates a default swap area of 512 MB for a UFS root environment. In a ZFS root environment, the default swap size is generally in the 512 MB to 2 GB range.
For general guidelines on allocating swap space, see Planning for Swap Space.
You can allocate additional swap space to the system by creating a swap file in a UFS root environment. Swap files are not supported in a ZFS root environment. For information about creating a swap file, see Adding More Swap Space.
An entry for a swap device in the /etc/vfstab file contains the following:
The full path name of the swap slice or swap file on system with a UFS root file system or a 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.