Continued heavy demand for numbers in the Employment Second preference category has required the establishment of a Worldwide cut-off date for the month of July. This action has been taken in an effort to hold number use within the annual numerical limit. Should there be an increase in the current demand pattern, it may be necessary to make this category completely “unavailable” prior to September 30, 2012.

The China and India Employment Second preference categories are already “unavailable”, and will remain so for the remainder of the fiscal year.
 
For more details, please see: http://travel.state.gov/visa/bulletin/bulletin_1360.html