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Determine Number of Blocks Corrupted
You have a database. You have a datafile and some blocks are corrupted in the datafile. What statement will you issue to know how many blocks are corrupted?
kunal1017
- Apr 1st, 2008
you can use the DBVERIFY utility to check the corruption in datafiles so that you can now number of blocks corrupted.Here is the procedure :On o/s prompt login as oracle user : $ dbv file= &...
hemant.agarwal03
- Mar 12th, 2008
You can check the "V_$DATABASE_BLOCK_CORRUPTION" view to determine the corrupted blocks.
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Disk (sort) Ratio
The ratio of disk (sort) is high. Is that good or bad? Why? How will you reduce disk sort?
rajendra_thanekar
- Apr 17th, 2008
Hi,Disk(sort)ratio is high is not good.Please set sort_area_retained_size and sort_area_size so that session can sort in max in memory.
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Oracle Snapshot too old error
What is Ora1555 error. Snapshot too Old error. Explain in detail.
jryan999
- May 1st, 2008
Oracle Rollback Segments (Undo more recently) hold a copy of data before it was modified, and they work in a round-robin fashion. Writing and then eventually overwriting the entries as soon as...
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How to know which query is taking long time?
pabroy
- May 5th, 2008
You can search Top ten sql.Top 10 Sql. SELECT *FROM (SELECT rownum,Substr(a.sql_text,1,200) sql_text, Trunc(a.disk_reads/Decode(a.executions,...
senthilora
- Sep 24th, 2007
You can use STATSPACK to take SNAPs while running those queries and get the report with details of SQLs taking more time to respond.
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Oracle Table space used and unused space
I have to check used space/unused space in table space. Which view /command will provide me the desired answer.
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Oratab file
What is stored in Oratab file
mandarkelkar
- Jun 5th, 2008
This file is used by ORACLE utilities. It is created by root.sh and updated by the Database Configuration Assistant when creating a database.A colon, ':', is used as the field terminator...
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What is row chaining
deepikadba
- Jun 7th, 2008
If a datablock is not able to store a complete row due to its less size then a row is store in another blocks & address of that row is stored in the previous block.it degrade performance of a database & there r more IOS generated.
sandhya
- Jun 27th, 2005
If any of he empty row is not sufficient to hold the row. then row is placed in multiple blocks. it happenes when the block size is small and rows are of large size. then it cause chaining. Due to chaining performance degrades and will cause more IOs
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Schema Procedure and Data
Schema A has some objects and created one procedure and granted to Schema B. Schema B has the same objects like Schema A. Schema B executed the procedure like inserting some records. In this case where the data will be stored whether in Schema A or Schema B?
shuklad
- Jul 6th, 2008
Procedure will be executed with the authority of A and therfore data will go to the tables owned by A. If one wants the data to go to B, use the clause authid current_user while defining the procedure.
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Execute Analyze Table Command
In which situation whether peak time or off peak time you will execute the ANALYZE TABLE command. Why?
harisivati
- Jul 13th, 2008
Gathering statistics can be very resource intensive for the server so avoid peak workload times to gather stale stats or Analyze Table .
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What is an index and How it is implemented in Oracle database
harshasp
- Jul 16th, 2008
Index is an object in the oracle database used to speed up the performance of the queries ie. it improves the access speed and response of query will be good when the query makes use of Index.ThanksHarsha
ramesh khanna
- Jun 27th, 2005
Index is a object to fetch the data fast and where class in the sql can be used to use the index
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Resize Tablespaces
Is it possible to resize tablespaces and data files? If yes, how?
nafees
- Jul 22nd, 2008
Hi all,Yes i agree with the answer but resize in the sense,the size should also get decrease.we can decrease even the size of the datafile but the condition is the datafile should be empty.
rajendra_thanekar
- Jun 25th, 2008
hi,We can resize the datafiles which in turn resize the tablespace for which the datafile belongs. The command is alter database datafile '<datafile_name>' resize(size)M;By this co...
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Import Export Utilities
How does one use the import/export utilities?
nafees
- Jul 22nd, 2008
Logical Backup using export utility works as an alternative backup method.we can export from one user and import into another within the same database.we can export from one database and import into a...
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Physical Standby Database
Outline the steps required for physical standby database creation?
nafees
- Jul 21st, 2008
Hi all,IT IS POSSIBLE WITH THE HELP OF DATA GUARD.To create a physical standby database ,the standby databse should be in MRM(Managed recovery mode)Let we proceed with an example, let ...
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What are the characteristics of data files
srinivasanram2004
- Jul 29th, 2008
Characteristics of a Data File : - A Data file can be associated with only one tablespace. - Once created, a datafile can be increased or decreased in size with RESIZE command. Example: ALTER da...
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Scenarios for rebuilding indexes
What are the different scenarios for rebuilding indexes...
chandubtech
- Aug 2nd, 2008
Actually you need to rebuild the indexes for 2 main scenarios.1)deleted entries represents 20% or more of the current entries2)the index depth is more than 4 levelsOracle index nodes are not deleted p...
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Accessing Dual Table
Explain Dual table. Is any data internally stored in dual table. Lot of users are accessing select sysdate from dual and they getting some millisecond differences. If we execute SELECT SYSDATE FROM EMP; what error will we get. Why?
abdulraheem_ar
- Aug 5th, 2008
Dual is a system owned table created during database creation. Dual table consist of a single column and a single row with value xWe will not get any error if we execute select sysdate from scott.emp?...
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Export query question
exp userid=system/manager file=expfile.dmp log=expfile.log full=Y compress=Y buffer=1000000If i do't mention compress & buffer parameter , then this query will run/not.
nafees
- Aug 10th, 2008
Yes, exactly it will run perfectly because compress and buffer both are optional.
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Differentiate file using filename
Three users at a time giving the following command: alter database backup controlfile to trace; How can you differentiate the file using the filename itself?
baala
- Aug 11th, 2008
When you issue the command "alter database backup controlfile to trace ; " a trace file will be created in the user_dump destination.The default name of the trace file would look something similar to ...
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Cost Based Optimizer and Rule Based Optimizer
What is the difference between Cost Based Optimizer and Rule Based Optimizer?(CBO is the default optimizer)
ajay.ocp
- Aug 20th, 2008
In brief the rule-based method means that when executing a query the database must follow certain predefined rules and matter what data is stored in affected database tables. The cost-based method mea...
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Identify Datafile in Backkup Mode
When you execute: alter tablespace begin backup; How can Oracle engine can identify that the corresponding datafiles are in backupmode?
Oracle DBA Interview Questions
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