ORA-12537 TNS: Connection Closed

Hello Everyone,

Today our developers were getting the error "ORA-12537 TNS: Connection Closed" where as i was able to connect to the database locally. But none of the external connection is accepted.

I did the below initially.

- Bounced both apps and db listner
- Checked mount points
- Provided full permission to /var/tmp/.oracle

But none of them fixed my issue. i went to $TNS_ADMIN and check all the below files,

listner.ora, tnsnames.ora and sqlnet.ora

I found the below parameters in sqlnet.ora and guessed this must be causing the error. Finally i commented both the parameters and bounced the listner. There error were no more.

#tcp.validnode_checking = yes
#tcp.invited_nodes=(*********.*****.com)  --> This parameter will not allow any other machine to be connected to db except the mentioned node or ip.

After commenting these parameter developers were able to make connection. But double check in your environment before you commenting out this parameter.

Thanks!