Resolution: If your Manager appears to run out of memory, and an out of memory error is printed to the Manager log, you may need to increase the Java heap size. This would typically only happen if the Manager is running many Jobs with many inputs (such as more than 40,000).
The Java maximum heap size is set in the server.sh or server.bat file, and is 512 MB by default in GridServer 4.2, and 1024 MB by default in GridServer 5.0 (it's 384 MB in GridServer 4.0, 128 MB in GridServer 3.2). It can be increased by changing the environment variable MAX_HEAP in the server.bat or server.sh file.