How to increase /tmp size in solaris ?

You can Increase the tmp space by adding a new and big swap file.

To add a swap file, follow these instructions:

Syntax: mkfile sizeoffile // => it creates a swap file
bash-2.05#mkfile 1500m /opt/myswapfile

Syntax: swap -a /path/file => adds the swap file
bash-2.05#swap -a /opt/myswapfile

To view the added swap file:
swap -l => view added swap file

Note :
bash-2.05# which mkfile
bash-2.05# which swap