Syllabus for AIIMS PG exam for MDS below.

https://www.aiims.edu/aiims/academic/aiims-syllabus/Syllabus%2520-%2520md%2520ms%2520mds%2520mha.pdf&ved=2ahUKEwjowYOc4OTdAhUSbo8KHdgsA4cQFjABegQIBxAB&usg=AOvVaw3xkLtMpLr2YW8XZLDC6LvE

Exam is conducted twice year in January and July with total of 200 MCQ and 3hours duration. Has negative marking of 0.333.

For entire exam pattern you may check bekow with eligibility criteria and expected dates. 

https://medicine.careers360.com/articles/aiims-pg-exam-pattern