TNS-12531: TNS:cannot allocate memory

I found this message in my listener.ora file while investigating a ORA-00600 error which was causing the database to slow down very much.

24-FEB-2015 11:55:00 * 12531 TNS-12531: TNS:cannot allocate memory 24-FEB-2015 11:55:02 * 12531 TNS-12531: TNS:cannot allocate memory 24-FEB-2015 11:55:04 * 12531 TNS-12531: TNS:cannot allocate memory

The reason which I found was that this database server was a 32-Bit Windows machine where maximum 4G RAM can be utilized. Once all RAM is consumed, listener would not be able to spawn a new server process because of memory shortage. In shortage of resources (especially on 32-bit platform), you may also face ORA-04030. Solution for this problem is to move to 64-bit platform. As a workaround, you can try to reduce SGA memory allocation to free up some memory and/or stop any unnecessary process or application.