Toad World® Forums

ORA-12571 TNS:packet wrtie failure


I get the error “ORA-12571 TNS:packet wrtie failure” when I try to execute the explain plan for a selected sql statement. The db raises ORA-00600 internal error code that is not visible to me. Our DBA had told me about this error. The DB got corrupted and had to be restarted.

The last sql before the error occured was:
where OWNER IN (:owner, ‘PUBLIC’)

  • Oracle 9i Enterprise Edition Release
  • SQL Navigator
  • SQL Optimizer
  • Oracle Client


The SQL you saw is the one we used to check if there is any db links defined in your database and it shouldn’t cause the error. You may verify this by running the SQL a few times in SQL*Plus to see if it will cause any problem.

The “ORA-12571 TNS:packet wrtie failure” error can be caused by unstable network or when the server is unavailable. I suggest you try repeat what you were doing to see if the problem is repeatable. I can take a closer look if it is repeatable.


I have read about that it might have something to do with a desktop firewall or an antivirus software interferring with db communication. I tried it with both deactivated but the problem still exists.

How about the SQL run in SQL*Plus or Toad? Does it get the same problem or the same problem happen in other PC?


Tony Ng

Old post, I know, but I’m getting the same error trialling this software.
My sql works fine in sql*plus and Toad 10.6 with the same tns connection.
I’m using Optimizer 8.5(1825).

Hi Graham,

I am sorry that we missed your post and hence not replying earlier.

Do you still experience the same problem? If yes, please provide the followings for us to investigate the problem:

  1. Support Bundle

    • Launch Optimizer,
  • Click on Help | Support Bundle (this will create another tab called Support Bundle for you)

  • Click Connect to open the Connection Manager

  • Connect to your database first

  • If the problem ocurred, go back to the Support Bundle tab to save and send back the Support Bundle files

    • If there was no error, repeat your steps to reproduce the error and send back the Support Bundle once the error is repeated.
  1. Steps to reproduce the problem.

    • Please send back the steps that will reproduce the problem.
    • Also let us know if the problem is reproducible when you connect in Connection Manager or only when you optimize or only in your steps
    • Let us know if it occurred occasionally or 100% of time.