Kernel doesn't free Cached Memory

[Vinicius <jdob@ig.com.br>]

Hi all! 

   I have a server with 2 Pentium 4 HT processors and 32 GB of RAM, this 
server runs lots of applications that consume lots of memory to. When I stop 
this applications, the kernel doesn't free memory (the  memory still in use) 
and the server cache lots of memory (~27GB). When I start this applications, 
the kernel sends  "Out of Memory" messages and kill some random 
applications. 

   Anyone know how can I reduce the kernel cached memory on RHEL 3 (kernel 
2.4.21-32.ELsmp - Trial version)? There is a way to reduce the kernel cached 
memory utilization? 

Thanks in advance (sorry my bad english). 

Vinicius. 
Protolink Consultoria.