Vlad_567,

не знаю, может в настройках оракл-клиента дело. Вот можно было бы покрутить какой-нибудь из параматров и посмотреть. Я бы начал с TCP.CONNECT_TIMEOUT :

https://docs.oracle.com/cd/E18283_01/network.112/e10835/sqlnet.htm
SQLNET.INBOUND_CONNECT_TIMEOUT
Default 60 seconds
To specify the time, in seconds, for a client to connect with the database server and provide the necessary authentication information.

SQLNET.OUTBOUND_CONNECT_TIMEOUT
Default None
To specify the time, in seconds, for a client to establish an Oracle Net connection to the database instance.

SQLNET.RECV_TIMEOUT
Default None
To specify the time, in seconds, for a database server to wait for client data after establishing a connection. A client must send some data within the time interval.

SQLNET.SEND_TIMEOUT
Default None
To specify the time, in seconds, for a database server to complete a send operation to clients after establishing a connection. Setting this parameter is recommended for environments in which clients shut down occasionally or abnormally.

TCP.CONNECT_TIMEOUT
Default 60 seconds
To specify the time, in seconds, for a client to establish a TCP connection