When the Oracle server is running on Windows and in dedicated connection mode, the client cannot be connected when the number of client connections reaches a certain value (about 400. At this point, the client typically gets a ora-12518 error.
After some searches on the Internet and actual tests, it is proved that this is not an oracle problem, but a Windows platform memory limit problem! This memory limit should be the memory running space of all Oracle processes (Private byte + outer shared byte), not simply the virtual memory size that Windows Task Manager can see, but should also contain Oracle and otherProgramShared memory space!
Therefore, there are three solutions to this problem:
1: Windows 32-bit awe,
2: Windows 64-bit Platform
3: Linux platform
In the shared connection mode, there can be more than 1000 connections. observe that the memory usage of Oracle does not meet the Windows Memory limit, but the number of connections on the client cannot be reached !!!