[error]: ORA-12516: TNS:listener could not find available........

[trakal]

Hello all readers,
I have a question concerning an error that i really want to understand.
I have an application client (C#) that connect to an Oracle server. Normally, it work good but just this morning, i have an error that the message is like below.
ORA-12516: TNS:listener could not find available handler with matching protocol stack.
I didn't do anything just do someelse and after maybe 1hours, i try to connect to Oracle database again and it worked. And now i have again this error message.
Can you give me any idea for that?
i want to know why this error and the cause from.
and how can i solve this problem?
Thanks before hand.

[debasisdas]

ORA-12516: TNS:listener could not find available handler with matching protocol stack
Cause: None of the known and available service handlers for the given SERVICE_NAME support the client's protocol stack: transport, session, and presentation protocols.
Action: Check to make sure that the service handlers (e.g. dispatchers) for the given SERVICE_NAME are registered with the listener, are accepting connections, and that they are properly configured to support the desired protocols.

[trakal]

Hello,
As i explained my problem in the last message. In fact, it work good for the connection etc. But yesterday morning, it show me this error. After, i waited maybe one hours, it re-work. and this problem is arrived since yesterday till now, i mean that it work and not work, after waiting a moment it re-work again...That why, i want to understand that.
Sorry if i can not explain clearly with my poor english. Thanks in advance.