Shutdown was hung with these messages in the alert log:

SHUTDOWN: waiting for active calls to complete.

*** 2015-12-22 10:59:09.298

SHUTDOWN: waiting for active calls to complete.

Why its happned?

The message "SHUTDOWN: waiting for active calls to complete" typically appears in the database alert file. This message indicates that the Oracle Database is in the process of shutting down, but it is waiting for existing connections or active sessions to complete their ongoing tasks before it can completely shut down.

When you initiate a shutdown of the database, the DBMS tries to ensure that all ongoing transactions are completed or rolled back properly to maintain data integrity. If there are active connections or sessions that are still performing operations, the shutdown process will wait for those operations to finish before it can finalize the shutdown.

Here are a few points to consider:

1. **Patience:** Depending on the nature of the active operations and their progress, the shutdown process might take some time to complete. Be patient and allow the system to finish its activities.

2. **Identifying Active Sessions:** It's a good idea to monitor the active sessions on the database using management tools like Oracle Enterprise Manager or SQL queries. This will help you understand what tasks are causing the shutdown delay.

3. **Emergency Shutdown:** If you need to shut down the database immediately and cannot wait for active sessions to complete, you might need to perform a forced or emergency shutdown. However, this should be a last resort, as it can potentially lead to data corruption or loss.

4. **Investigating Long-Running Transactions:** If you frequently encounter delays during shutdown due to long-running transactions, you should investigate the cause. This might involve optimizing queries, tuning the database, or redesigning certain processes to prevent such delays.

5. **Graceful Shutdown:** Whenever possible, try to perform a graceful and planned shutdown of the database during maintenance windows to allow ongoing tasks to complete normally.