Respected Asha,
Manpower problems can mean differnt things, first and foremost, you have to review your company policies and find out faults. There has to be a reason why these employees are unsatisfied, try and speak to them individually. Try and set surveys or interviews interacting with them on an individual basis to understand the root of the problem. Remember 1 thing being an HR is being diplomatic. Diplomatically take out info from these employees themselves. And about the survey, try and conducts it in a format of the exit interview, then only you would get the required info. An organization and its HR should be open to criticisms in order to evaluate its Policies

Increment depends on your company policies. Usually there are Annual or Semi-annual increments. As mentioned, increments depends on the results of the PMS. Usually it is a percentage which is calculated on the basis of various parameters which indicated your performance. Usually a slab made for the different parameters in the the performance/productivity variability. say for instance for a person who's productivity was 60% compared to the set KPAs, his increment would be 8%, now someone with 90% gets 12%, another with 100% gets 15%. At times you would have certain employees scoring above 100%, for these employees, a special increment is set which is added to the 15% increment, being 15% the slab for 100% efficiency. usually another 10% max increment is added to the incremented value....... This is the usual trend, again it depends from one company to the other my friend.

Thanks,
Kevin