An unexpected ORA-12520

Problem description: a few days ago, I was temporarily informed that a set of applications that had been running for many years could not connect to the database, but it was normal in the morning. The ora-12520 error was reported through netmanager,pl/sql and sqlplux xx/xx@service_name testing on the database server. The database did not make any other settings, and the application server did not make any changes.

Environment: oracle 10.2.0.4 rac+sun system

Handling method:

1. Connect to the database server to check that there is no problem with the listening of the two nodes (lsnrctl status found that the instance has been registered for listening).

2. There are only a few dozen process,session checks.

3. Check the database server remote_listener,local_listener parameters (for caution).

4. Check the cluster service to find the listening service offline of the two nodes, and notify crs_start ora....C1.lsnr to start the listening service. Through sqlplus xx/xx@service_name or ora-12520.

After the completion of the above inspection, I can not think of what caused it?

After the last two nodes are restarted, the application can connect to the database normally.

Later, when I called the business side to communicate, it was reported that they did some work on the Internet in the afternoon (I don't know what it was).

Question: when dealing with the above four steps, the network is normal. Even if there is a network problem before, why the network is normal and still can not access the database.