How Swap Space Is Allocated

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 Mbytes for a UFS root environment. In a ZFS root environment, the default swap size is generally in the 512 Mbyte to 2 Gbyte 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. For information about creating a swap file, see Adding More Swap Space.

Swap Areas and the /etc/vfstab File

After the system is installed, swap slices 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 slice or swap file

• 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.