When I am using APS for PSS (shooting Method) using swap file, APS is being disbled.
How can prevent APS being disabled.
The answer is simple; don't use swapfile. Swap file was an option added a long time ago to increase the capacity of SpectreRF when memory was a lot more expensive than it is now, and there was no 64 bit version of spectre. Nowadays you'd be far better off using 64 bit spectre if you need the capacity.
It always had a negative effect on performance because it had to write all the information calculated during the shooting interval to disk - which could be a lot of data. In the past if you really needed to use this you should only use it if absolutely necessary and then make sure that the swapfile was on a local (not networked) disk.
Now, turn on 64 bit either via the option on the setup->environment form or by typing -64 in the userCmdLineOption field on that form.