DataGaurd

 1) If I resize or added a datafile in Primary, but in DR there is no space to get added same size, what is the fix?

https://www.forum.dbagenesis.com/forum/oracle-database-administration/adding-datafiles-on-primary-when-you-don-t-have-sufficient-space-left-on-standby-database

https://gavinsoorma.com/2009/06/resize-standby-datafile-if-disk-runs-out-of-space/

https://rajeevjhaoracle.wordpress.com/2012/11/01/unnamed-file-error-in-standby-after-adding-new-file-to-primary-database-ora-01111-ora-01110-ora-01157/

2) What is archive_lag_target ?

3) Real Time Apply ?

4) How to check archive log gap ?

5) which process will ship the redos/archives from primary to standby ? NSA

6) How to use standby backup to rrestore a primary db ?

7) 

EXPORT - IMPORT

 Do we have to use same number of parallel in export and import ?

On what basis is parallel used ?

--> For Data Pump Export, the value that is specified for the parallel parameter should be less than or equal to the number of files in the dump file set.  Data Pump Import should not have a value for the PARALLEL parameter that is significantly larger than the number of files in the dump file set.

how to increase the performance of export /import ?

-----------------------------------------------------
-- Set the degree of parallelism to two times the number of CPUs, then tune from there.
-- For Data Pump Export, the PARALLEL parameter value should be less than or equal to the number of dump files.
-- For Data Pump Import, the PARALLEL parameter value should not be much larger than the number of files in the dump file set.

Can we get a dumpfile of a particular size?

How to take certain amount of data backup from a table ?

Encrypted export and import ?

Does archive gets generated during export and import ? If yes, in case a lot of archive is getting generated then what do we do ?

Is UNDO tablespace used during export and import?

Is TEMP tablespace used during export and import ?

How to stop archive log generation while import is running ?

In schema refresh, will be dblinks be copied ?

What is direct=y in export and import?

can we refresh and entire database new/existing using full=y   ? 

When I drop a 1 TB table where does it reside ?

which tablespace it takes while dropping a table ?

Snapshot too old error during export/ import ?

How do I stop archiving in Oracle ?

How to kill- start/stop , decrease/increase parallel in export/import?

If we want to export only 1000 roes of table during export ? what is the command?

How is the CPU used when running export and import?

When we run an export/import how do we know which process is running which data ?

Patching Questions

1) If we find any conflicts in One-Off Patches ? --> We will rollback the patch and get the alternate patch from Oracle and then we will apply it.

2) RAC database patching differences as compared to a single node?

--> https://docs.oracle.com/cd/B16240_01/doc/em.102/e15294/rac.htm

3) Utility to apply patch --> Opatch 

4) Difference b/w PSU and One Off Patches?

5) Prechecks for One Off and Datapatches?

6) Before applying a Patch how do we know if its going to be successfull --> 

   Optach prereq checkconflictagainstOHwithdetails  -ph ./

7) Opatch utility 

8) How to rollback a Oneoff patch or PSU ?

9) What to do if a PDB goes to restricted mode after patching ?

   -->  select * from pdb_plug_in_violations

10) After db upgrade users report login issues / password expired ,-> 

   sqlnet.ora --> allowed logon versions server // client   = 8

Performance Questions

1)  What is log sync wait event ?

2)  AWR reports ? 

      --> What are the things you check for in an AWR report ?

      --> Where do you check for issues in an AWR report ?

3) To 10 wait events , and how do you resolve them ?

4) Batch job was running fine till yesterday, today its taking long. What are the things you will check for?

5) When do indexes become invalid ?

6) For regular jobs why the Hash-Plan-Value gets changed suddenly and job takes long time ?

7) What are the things you check for when user's complain of performance issues ?

8) What is an explain plan and what do you check in it to resolve performance issues ?

9) What is ASH and what can we get from it? What is the difference between AWR and ASH ?

10) I have a 20GB of update/insert statements and my SGA is only 5 GB . How does it work ?

11) How do avoid parsing ?

12) Query is running slow. Can we force to change the execution plan ?

13) WAIT events , Type of wait events and locks and types of locks ?

14) How is a query PARSED in oracle database ?

15) Type of Optimizers and what it does ?

16) If an user executes SELECT/INSERT/UPDATE at a time, which one is executed first.

17) Can I drop a table if a user is already running an insert/update/delete on same table?

18) How ALTER/SELECT/DROP/CREATE works -- will there be any UNDO TBS usage for DDL?

19) How do you find TOP WAIT events in Oracle ?