Oracle DBA Interviews Questions and Answers

Oracle Apps DBA Questions:
1)I am applying a patch , can I open another session and run adadmin ?

Answer: Yes, unless you are running a process where workers are involved

2)I am applying a patch , can I open another session in another node and run adpatch?
Answer: No, We should not do.

3)When database is up, listener is up. Listener.ora and tnsnames.ora both are configured properly, still client is not being able to make a connection to the database. What may be the possible reson?
Answer: Check sqlnet.ora and see the client IP Address information is available
tcp.validnode_checking = yes
tcp.invited_nodes = (hostname1, hostname2)

4) Can C driver be applied when database is down?
Answer: No, for any patch you are applied authentication is mandatory.
5)If users complain they cant see the login page , how you will debug the issue? 
Answer: Check whether apache is running (ps –ef |grep http), u can also check apache log file.
6)Is it possible to clone a database from hotbackup?
Answer: yes, of course.

7)When your applying a patch in test mode, does it generate log file?
Answer: Yes, It should be, but never checked.

8)Output & logfiles for requests executed on source instance not working on cloned instance??
Answer: We can Check whether apps listener is running

9)What happens if you don’t give cache size while defining concurrent manager?
Answer: Most often when …a request goes "inactive/no manager" and is then processed a short time later, the solution is to either increase the cache size for your Standard manger, or increase the actual number of Standard Manager processes that can run. Cache Size is set in the Concurrent/Manager/Define form. Basically, this regulates how many requests a manager will pick up for each sleep cycle.

Increasing the cache size within reason allows you to decrease the sleep cycle. In turn, your managers will wake up and scroll through the tables less frequently, which reduces the amount of work they have to do as well as the amount of system resources utilized. We see sleep cycles set to 5 seconds at some customer sites and recommend increasing the value, since the managers are waking up and re-reading the same table far too frequently. For reports that for the most part take a minimum of 1 minute to run, the queue wakes up 12 times to check for runnable processes before even one running request completes.

10)If users are unable to see the output of their concurrent requests , what could be the reason?
Answer: Apps listener is not running .

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All answers are my own or copied from other sites, I really appreciate if anybody can suggest a better answer.

Thanks.