ORA-12520 error after Oracle RAC upgrade

Symptom:

After Oracle10gR2.0.0.1 is upgraded, A ORA-12520 error is reported for client connection now

12520,000 00, "TNS: listener cocould not find available handler for requested type of server"
// * Cause: None of the known and available service handlers for requested type
// Of server (dedicated or shared) are appropriate for the client connection.
// * Action: Run "lsnrctl services" to ensure that the instance (s) have
// Registered with the listener and that the appropriate handlers are
// Accepting connections.

Solution:

After finding information on the Internet and modifying the following parameters, it is normal:

SQL> alter system set local_listener = '(ADDRESS = (PROTOCOL = TCP) (HOST = 172.0.2.62) (PORT = 1521 ))'
2 scope = spfile sid = 'rac11g1 ';
The system has been changed.
SQL> alter system set local_listener = '(ADDRESS = (PROTOCOL = TCP) (HOST = 172.0.2.63) (PORT = 1521 ))'
2 scope = spfile sid = 'rac11g2 ';
The system has been changed.
SQL> shutdown the immediate database has been disabled. The database has been detached.
The ORACLE routine has been disabled.

SQL> startup
The ORACLE routine has been started.
Total System Global Area 1.7108E + 10 bytes
Fixed Size 2101632 bytes
Variable Size 3814182528 bytes
Database Buffers 1.3288E + 10 bytes
The Redo Buffers 4431872 bytes database has been loaded. The database has been opened.
Another Node also restarts the database server.
SQL> conn system/test @ rac is connected.

Solve the problem.

In addition, after the database is patched, the following error occurs when the database is started:

SQL> startup
ORA-00119: invalid specification for system parameter LOCAL_LISTENER
ORA-00132: syntax error or unresolved network name 'listener _ ge02'

The solution is as follows:
1. Shut down the database;
SQL> shutdown abort
ORACLE instance shut down.

2. In the/opt/oracle/product/10.2.0/network/admin/tnsnames. ora file, add the following statement:
LISTENER_GE02 =
(ADDRESS = (PROTOCOL = IPC) (KEY = EXTPROC0 ))
3. Restart the database.
SQL> startup
ORACLE instance started.
Total System Global Area 285212672 bytes
Fixed Size 1218992 bytes
Variable Size 92276304 bytes
Database Buffers 188743680 bytes
Redo Buffers 2973696 bytes
Database mounted.
Database opened.