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Causes of ORA-12571 TNS packet writer failure error

We are using Oracle 9i version 9.2 on Windows platform. Yesterday on a client running on Windows 2000 Professional,...

this error came: "ORA-12571 TNS packet writer failure." I looked for the solution on Internet and found several different responses. Someone says it's a spyware; someone else says Oracle server has blocked this particular IP address so I should just restart the server and it will be okay; someone says to remove the TCP/IP protocol from the client and again reinstall the protocols. My problem was solved, though, by removing the spy.

But I want to ask, what's the real meaning of this problem and what is the proper solution for this.

Unfortunately, the ORA-12571 error message is a catch-all message. There could be many reasons why you will receive this error. Basically, this error means that the network communication with your TCP/IP protocol was severed for some unknown reason. There could be many reasons why your network communication to the database was severed. Your NIC card in your workstation could have died. Your network cable could be cut. Your ISP could have momentarily dropped all active connections. Your cable modem could have been rebooted. Software could be disrupting your communications (which appears to be your case). So you have the daunting task of making sure that your TCP communications between your application and the database are not disrupted. How do you best achieve this task? You'll have to troubleshoot the problem with any and all tools. First, I'd fire up a web browser and see if I can connect to web sites. Then, I'd try to ping my database server. Then I'd try to tnsping the Oracle listener. Each time you try something, if you do not achieve desired results, then you have a better idea of where your problem lies. If all of the above still works, then you can examine software problems. Your last course of action is to start a network trace of Oracle's Net software and then send the trace files to Oracle Support once the problem is duplicated.

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