How to drop caches memory on EL4U7 or onward

To reclaim caches, please do as following: .
Action plan
===========
- Sync the data to disk:
# sync

- # echo 3 >/proc/sys/vm/drop_caches

E.g:
1, # free
            total       used       free     shared    buffers     cached
Mem:        604852     119048     485804          0      11676      57768
-/+ buffers/cache:      49604     555248
Swap:      2097144          0    2097144

2, #sync

3, # echo 3 >/proc/sys/vm/drop_caches
Note: There has a space between number "3" and ">"

4, # free
            total       used       free     shared    buffers     cached
Mem:        604852      61320     543532          0        184      12312
-/+ buffers/cache:      48824     556028
Swap:      2097144          0    2097144

As above output shows that about 80% cached memory has been reclaimed 57768-12312 KB.

Cheers,
Terry