Problem with memory while calling Oracle Cursors

We have two interfaces which are calling Oracle cursors. The memory allocated to our server is 750 MB and a total of 8 interfaces are running on this server. Untill these two services are running our memory usage is in 50’s but as soon as these two services are enabled and are executed, the memory is going to 90’s and reaching 100% after sometime. we did not have this problem in 6.1 version. Only when our server was upgraded to 6.5 with the same code, we are facing this issues. Please suggest if we have to apply any patches in 6.5 if we are using Oracle stored procedures and cursors which can resolve this issue.

Thank You