Oracle Database B10772-01 Administrator's Manual page 199

Action: Check the following:
Ensure that the correct wallet location is specified in the sqlnet.ora file
so the system can find the wallet.
Use Oracle Net Manager to ensure that cipher suites are set correctly in the
sqlnet.ora file. (Sometimes this error occurs because the sqlnet.ora
has been manually edited and the cipher suite names are misspelled. Note
that case sensitive string matching is used with cipher suite names.)
Use Oracle Net Manager to ensure that the SSL versions on both the client
and the server match, or are compatible. Sometimes this error occurs
because the SSL version specified on the server and client do not match. For
example, if the server accepts only SSL 3.0 and the client accepts only TLS
1.0, then the SSL connection will fail.
For more diagnostic information, enable Oracle Net tracing on the peer.
ORA-28865: SSL Connection Closed
Cause: The SSL connection closed because of an error in the underlying
transport layer, or because the peer process quit unexpectedly.
Action: Check the following:
Use Oracle Net Manager to ensure that the SSL versions on both the client
and the server match, or are compatible. Sometimes this error occurs
because the SSL version specified on the server and client do not match. For
example, if the server accepts only SSL 3.0 and the client accepts only TLS
1.0, then the SSL connection will fail.
If you are using a Diffie-Hellman anonymous cipher suite and the SSL_
CLIENT_AUTHENTICATION parameter is set to true in the server's
listener.ora file, then the client does not pass its certificate to the server.
When the server does not receive the client's certificate, it (the server)
cannot authenticate the client so the connection is closed. To resolve this use
another cipher suite, or set this listener.ora parameter to false.
Enable Oracle Net tracing and check the trace output for network errors.
See Actions listed for
ORA-28868: Peer Certificate Chain Check Failed
Cause: When the peer presented the
check failed. This failure can be caused by a number of problems, including:
One of the certificates in the chain is expired.
"ORA-28862: SSL Connection Failed"
certificate
Configuring Secure Sockets Layer Authentication 7-33
Troubleshooting SSL
on page 7-32
chain, it was checked and that