For the latest version of Oracle 12c database, we will encounter many problems in the process of installing and building the database. Here I will summarize the problems I encountered, and give the corresponding solutions.

1.ORA-12500: TNS: Listener could not start the dedicated server process
As the name implies, this type of problem relates to the associated listening service

sqlplus/noolog
nn /as sysdba
s>up
conn /as sysdba
startup
conn /as sysdba
startup ORCL database associated with the service, if not opened in the CMD check can be through the task manager in the service column to find the relevant service to open the restart, ORACLESSWrite – ORACLESService – Listener – ORACLEScheduler -, generally is one of the service and Listener did not start, the service can be resolved after the restart. To reconfigure listeners, open the Net Configuration Assistant and reconfigure existing listeners. Open the netmanager and check whether the user’s localhost port 1521 is not abnormal.

ORA-12560:TNS: Protocol oracer error
Error problems can be caused by three factors:
The listening service is not up.
Windows platform a operation as follows: Start – Program – Management Tools – Services, open the Services Panel, start OracleHome92TNSListener service. The database instance is not up.
Windows platform: Start – Programs – Management Tools – Services, open the Services panel, launch Oracle Server XXXX,XXXX is your Database SID. Registry problems.
regedit, then go to HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE\HOME0 and set the environment variable ORACLE_SID to XXXX. XXXX is your database SID. Or just to the right of My Computer, Properties — Advanced — Environment Variable — System Variable — New, Variable Name = ORACLE_SID, Variable Value =XXXX,XXXX is your Database SID. ORACLE_SID =XXXX. ORACLE_SID =XXXX. ORACLE_SID =XXXX.

3. Port occupancy problem
CMD to perform netstat ano | findstr searches in 1521 CMD perform netstat – ano find localaddress port
Query to the PID of the executing process
Taskkill /pid ** /f Open the services panel, find the running pid process and terminate it
End the process, and the occupied port will be released

4.ORA-12505 Listener refused the connection

sid, user name, etc. Make sure it matches the database you created — restart your computer, release the used port 1521 — restart Oracle Develpoer — then run CMD, open a command prompt, and type LSNRCTL to run stop first. Then start — Open Resource Manager
and run C:\ Oraclexe \app\ Oracle \product\10.2.0\ Server \BIN\tnslsnr.exe
ey_local_machine \ System \CurrentControlSet\Services\ OraclexetNSListener
I>Path key value: C: \ oraclexe \ app \ oracle \ product \ 10.2.0 \ server \ BIN \ TNSLSNR exe

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Temarily sorted out the above four problems, in general, to ensure that the associated monitoring service is normally opened, the server SID and other configurations are correct, can test the successful connection.