Problem with delay when switching a device between adapter and battery

[saurav_sdpl]

In the given schematic i am running the device mainly on adaptor , but in the absence of mains supply i am switching over to battery supply through mosfet.

But practically when i am testing the circuit ,during transistion from adaptor to battery it takes 2sec, during which i loose my important data saved in micro.

what could be the possible reason for this delay.

I am also using a boost regulator for battery powered supply

Its urgent plz help

 

[Borber]

Re: Schematic

Bad picture. Unreadable labels. Post it as gif and in greater resolution.