Interview Questions.

Question 1. What Is Performance Tuning?

Answer :

Making surest use of device the usage of existing resources referred to as performance tuning.

Question 2. What Are The Types Of Tunings?

Answer :

CPU Tuning
Memory Tuning
IO Tuning
Application Tuning
Database Tuning
Oracle DBA Interview Questions
Question 3. What Mainly Database Tuning Contains?

Answer :

Hit Ratios
Wait Events
Question 4. What Is An Optimizer?

Answer :

Optimizer is a mechanism so that it will make the execution plan of an square statement.

Oracle DBA Tutorial
Question five. What Are The Types Of Optimizers?

Answer :

RBO(Rule Based Optimizer)
CBO(Cost Based Optimizer)
Oracle RAC/ASM Interview Questions
Question 6. Which Optimizer Is The Best One?

Answer :

CBO

Question 7. What Are The Pre Requsited To Make Use Of Optimizer?

Answer :

Set the optimizer mode
Collect the data of an object
RMAN (Recovery Manager) Interview Questions
Question eight. How Do You Collect Statistics Of A Table?

Answer :

Analyze desk emp compute facts or analyze table emp estimate information.

Question 9. What Is The Diff Between Compute And Estimate?

Answer :

If you operate compute, The FTS will show up, if you use estimate just 10% of the table will be examine

Database Administration Interview Questions
Question 10. Data Dictionary Follows Which Optimizer Mode?

Answer :

RBO.

Question 11. How Do You Delete Statistics Of An Object?

Answer :

Analyze desk emp delete information.

Oracle Exadata Database Interview Questions
Question 12. How Do You Collect Statistics Of A User/schema?

Answer :

exec dbms_stats.Gather_schema_stats(scott)

Oracle DBA Interview Questions
Question thirteen. How Do You See The Statistics Of A Table?

Answer :

pick num_rows,blocks,empty_blocks from dba_tables in which tab_name=’emp’

Question 14. What Are Chained Rows?

Answer :

These are rows, it spans in multiple blocks.

Question 15. How Do You Collect Statistics Of A User In Oracle Apps?

Answer :

fnd_stats bundle.

SQLite Interview Questions
Question sixteen. How Do You Know What Sql Is Currently Being Used By The Session?

Answer :

By goind v$square and v$sql_area.

Question 17. What Is A Execution Plan?

Answer :

Its a road map how sq. Is being performed through oracle db..

Oracle DBA Troubleshooting Interview Questions
Question 18. How Do You Get The Index Of A Table And On Which Column The Index Is?

Answer :

dba_indexes and dba_ind_columns

Oracle RAC/ASM Interview Questions
Question 19. Which Init Parameter You Have To Set To Bypass Parsing?

Answer :

cursor_sharing=force

Question 20. How Do You Know Which Session Is Running Long Jobs?

Answer :

via going v$session_longops

Oracle Data Guard Interview Questions
Question 21. How Do You Flush The Shared Pool?

Answer :

regulate device flush shared_pool

Question 22. How Do You Get The Info About Fts?

Answer :

the usage of v$sysstat

Question 23. How Do You Increase The Db Cache?

Answer :

regulate table emp cache

Question 24. Where Do You Get The Info Of Library Cache?

Answer :

v$librarycache

RMAN (Recovery Manager) Interview Questions
Question 25. How Do You Get The Information Of Specific Session?

Answer :

v$mystat

Question 26. How Do You See The Trace Files?

Answer :

the usage of tkprof utilization: tkprof allllle.Trc llkld.Txt

Question 27. How Many Types Of Hits Are There And What Are They?

Answer :

There are  styles of hits, they're

Buffer hit
library hit
Database Administration Interview Questions
Question 28. What Are The Types Of Wait Events?

Answer :

cpu time
direct route study
Question 29. A Table Space Has A Table With 30 Extents In It. Is This Bad? Why Or Why Not?

Answer :

Multiple extents in and of themselves aren’t terrible. However in case you additionally have chained rows this may hurt performance.

Question 30. How Do You Set Up Tablespaces During An Oracle Installation?

Answer :

You must usually try to use the Oracle Flexible Architecture widespread or another partitioning scheme to make sure right separation of SYSTEM, ROLLBACK, REDO LOG, DATA, TEMPORARY and INDEX segments.

Question 31. You See Multiple Fragments In The System Tablespace, What Should You Check First?

Answer :

Ensure that users don’t have the SYSTEM tablespace as their TEMPORARY or DEFAULT tablespace venture by means of checking the DBA_USERS view.

Question 32. What Are Some Indications That You Need To Increase The Shared_pool_size Parameter?

Answer :

Poor records dictionary or library cache hit ratios, getting mistakes ORA-04031. Another indication is gradually lowering performance with all other tuning parameters the equal.

Question 33. What Is The General Guideline For Sizing Db_block_size And Db_multi_block_read For An Application That Does Many Full Table Scans?

Answer :

Oracle nearly usually reads in 64k chunks. The two ought to have a product same to sixty four or a multiple of 64.

Oracle Exadata Database Interview Questions
Question 34. What Is The Fastest Query Method For A Table?

Answer :

Fetch with the aid of rowid.

Question 35. Explain The Use Of Tkprof? What Initialization Parameter Should Be Turned On To Get Full Tkprof Output?

Answer :

The tkprof device is a tuning device used to determine cpu and execution times for SQL statements. You use it via first placing timed_statistics to real inside the initialization file after which turning on tracing for either the whole database thru the sql_trace parameter or for the session the use of the ALTER SESSION command. Once the hint report is generated you run the tkprof tool towards the trace record and then observe the output from the tkprof device. This also can be used to generate give an explanation for plan output.

Question 36. When Looking At V$sysstat You See That Sorts (disk) Is High. Is This Bad Or Good? If Bad, How Do You Correct It?

Answer :

If you get excessive disk sorts that is awful. This indicates you want to music the type region parameters inside the initialization files. The important kind are parameter is the SORT_AREA_SIZe parameter.

SQLite Interview Questions
Question 37. When Should You Increase Copy Latches? What Parameters Control Copy Latches?

Answer :

When you get excessive contention for the copy latches as proven by using the “redo replica” latch hit ratio. You can growth replica latches through the initialization parameter LOG_SIMULTANEOUS_COPIES to twice the variety of CPUs for your gadget.

Question 38. Where Can You Get A List Of All Initialization Parameters For Your Instance? How About An Indication If They Are Default Settings Or Have Been Changed?

Answer :

You can look in the init.Ora record for an illustration of manually set parameters. For all parameters, their value and whether or not or not the current cost is the default price, look inside the v$parameter view.

Question 39. Describe Hit Ratio As It Pertains To The Database Buffers. What Is The Difference Between Instantaneous And Cumulative Hit Ratio; Which Should Be Used For Tuning?

Answer :

Hit ratio is a measure of the way normally the database become able to examine a cost from the buffers verses how many times it needed to re-read a facts fee from the disks. A fee more than eighty-ninety% is ideal, much less may want to suggest problems. If you take the ratio of existing parameters this may be a cumulative price since the database started out. If you do a comparison between pairs of readings primarily based on a few arbitrary time span, that is the immediate ratio for that point span. Generally speaking an instantaneous reading offers more precious facts due to the fact that it'll inform you what your instance is doing for the time it become generated over.

Question 40. Discuss Row Chaining, How Does It Happen? How Can You Reduce It? How Do You Correct It?

Answer :

Row chaining happens when a VARCHAR2 cost is up to date and the duration of the brand new fee is longer than the vintage price and won’t suit within the ultimate block area. This outcomes in the row chaining to another block. It can be reduced via placing the storage parameters on the table to suitable values. It may be corrected by using export and import of the effected table.

Oracle DBA Troubleshooting Interview Questions
Question 41. When Looking At The Estate Events Report You See That You Are Getting Busy Buffer Waits. Is This Bad? How Can You Find What Is Causing It?

Answer :

Buffer busy waits might also indicate rivalry in redo, rollback or records blocks. You need to test the v$waitstat view to peer what regions are inflicting the hassle. The price of the “count number” column tells wherein the trouble is, the “elegance” column tells you with what. UNDO is rollback segments, DATA is data base buffers.

Question 42. If You See Contention For Library Caches How Can You Fix It?

Answer :

Increase the scale of the shared pool.

Oracle Data Guard Interview Questions
Question forty three. If You See Statistics That Deal With “undo” What Are They Really Talking About?

Answer :

Rollback segments and related systems.

Question forty four. If A Tablespace Has A Default Pct Increase Of Zero What Will This Cause (in Relationship To The Smon Process)?

Answer :

The SMON technique received’t routinely coalesce its unfastened area fragments.

Question forty five. If A Tablespace Shows Excessive Fragmentation What Are Some Methods To Defragment The Tablespace? (7.1,7.2 And 7.Three Only)

Answer :

In Oracle 7.0 to 7.2 The use of the ‘adjust session set activities ‘immediately trace call coalesce stage ts#’;’ command is the easiest manner to defragment contiguous unfastened area fragmentation. The ts# parameter corresponds to the ts# value located inside the ts$ SYS table. In version 7.3 the ‘alter tablespace coalesce;’ is first-class. If free space isn’t contiguous then export, drop and import of the tablespace contents may be the most effective manner to reclaim non-contiguous free area.

Question forty six. How Can You Tell If A Tablespace Has Excessive Fragmentation?

Answer :

If a pick against the dba_free_space desk indicates that the count of a tablespaces extents is greater than the remember of its records documents, then it is fragmented.

Question forty seven. You See The Following On A Status Report:
redo Log Space Requests 23
redo Log Space Wait Time zero
is This Something To Worry About? What If Redo Log Space Wait Time Is High? How Can You Fix This?

Answer :

Since wait time is zero, no. If wait time was high it might suggest a need for greater or large redo logs.

Question 48. What Can Cause A High Value For Recursive Calls? How Can This Be Fixed?

Answer :

A excessive fee for recursive calls is cause with the aid of improper cursor utilization, immoderate dynamic space control movements, and or immoderate announcement re-parses. You need to decide the reason and correct it By both relinking programs to preserve cursors, use right space control techniques (proper garage and sizing) or ensure repeat queries are placed in programs for proper reuse.

Question forty nine. If You See A Pin Hit Ratio Of Less Than zero.Eight In The Estate Library Cache Report Is This A Problem? If So, How Do You Fix It?

Answer :

This shows that the shared pool can be too small. Increase the shared pool size.

Question 50. If You See The Value For Reloads Is High In The Estate Library Cache Report Is This A Matter For Concern?

Answer :

Yes, you must strive for zero reloads if feasible. If you see immoderate reloads then boom the dimensions of the shared pool.

Question 51. You Look At The Dba_rollback_segs View And See That There Is A Large Number Of Shrinks And They Are Of Relatively Small Size, Is This A Problem? How Can It Be Fixed If It Is A Problem?

Answer :

A big variety of small shrinks shows a need to boom the dimensions of the rollback segment extents. Ideally you should have no shrinks or a small variety of massive shrinks. To restore this simply increase the size of the extents and modify most suitable as a result.

Question 52. You Look At The Dba_rollback_segs View And See That You Have A Large Number Of Wraps Is This A Problem?

Answer :

A massive range of wraps suggests that your volume length on your rollback segments are in all likelihood too small. Increase the scale of your extents to reduce the wide variety of wraps. You can observe the average transaction size inside the same view to get the information on transaction size.

Question 53. In A System With An Average Of 40 Concurrent Users You Get The Following From A Query On Rollback Extents:
rollback Cur Extents
r01 11
r02 eight
r03 12
r04 9
system 4
you Have Room For Each To Grow By 20 More Extents Each. Is There A Problem? Should You Take Any Action?

Answer :

No there isn't a hassle. You have forty extents showing and a median of forty concurrent customers. Since there may be masses of room to develop no motion is needed.

Question fifty four. You See Multiple Extents In The Temporary Tablespace. Is This A Problem?

Answer :

As long as they're all of the identical length this isn’t a problem. In fact, it is able to even improve performance for the reason that Oracle gained’t should create a new extent whilst a consumer desires one.