▎Common Oracle Errors and Fixes

1. ORA-12154: TNS: Could not resolve the connect identifier specified
Cause: Database connection string can't find the service name.
Fix: Check your tnsnames.ora file for typos or missing service names. Even a misplaced parenthesis can cause issues.

2. ORA-00600: Internal error code
Cause: A serious internal error occurred.
Fix: Review the alert.log and trace files for details. Use Oracle’s ORA-00600 Lookup Tool for deeper insights.

3. ORA-01722: Invalid Number
Cause: Attempting to convert a non-numeric string to a number.
Fix: Verify data types in SQL queries, especially with conversions like TO_NUMBER.

4. ORA-03113: End-of-file on communication channel
Cause: Sudden connection drops indicate network or server issues.
Fix: Investigate server crashes, network disconnections, or unexpected process terminations.

5. ORA-01000: Maximum open cursors exceeded
Cause: Too many open cursors without closing them.
Fix: Optimize your code to ensure cursors are closed and adjust the OPEN_CURSORS parameter if necessary.

6. ORA-12560: TNS: Protocol adapter error
Cause: Connectivity issue due to improperly running Oracle services.
Fix: Ensure Oracle services are active and verify your environment variables.

7. ORA-12505: TNS: Listener does not currently know of SID given in connect descriptor
Cause: Configuration mismatch with the listener.
Fix: Use lsnrctl status to check listener configuration and ensure the SID matches in listener.ora.

8. ORA-04031: Unable to allocate memory in the shared pool
Cause: Memory allocation issues in the shared pool.
Fix: Increase the shared pool size or flush it with ALTER SYSTEM FLUSH SHARED_POOL.

9. ORA-01555: Snapshot too old
Cause: Insufficient undo tablespace during undo operations.
Fix: Increase undo tablespace size or optimize queries to reduce excessive undo generation.

10. ORA-00936: Missing expression
Cause: Syntax errors in SQL statements.
Fix: Review SQL syntax for missing or misplaced operators, keywords, or parentheses.




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