Oracle DBA Interview Questions - An interviewhelper.org blog

If a view on a single base table is manipulated will the changes be reflected on the base table

2009-03-04T03:36:00.000-08:00

Question :If a view on a single base table is manipulated will the changes be reflected on the base table?
Answer :If changes are made to the tables and these tables are the base tables of a view, then the changes will be reference on the view.

Can a view be updated/inserted/deleted? If Yes - under what conditions

2009-03-04T03:34:00.000-08:00

Question :Can a view be updated/inserted/deleted? If Yes - under what conditions?
Answer :A View can be updated/deleted/inserted if it has only one base table if the view is based on columns from one or more tables then insert, update and delete is not possible.

What are the advantages of VIEW

2009-03-04T03:31:00.000-08:00

Question :What are the advantages of VIEW?
Answer :- To protect some of the columns of a table from other users. - To hide complexity of a query. - To hide complexity of calculations.

What is CYCLE/NO CYCLE in a Sequence

2009-03-04T03:30:00.000-08:00

Question :What is CYCLE/NO CYCLE in a Sequence?
Answer :CYCLE specifies that the sequence continue to generate values after reaching either maximum or minimum value. After pan-ascending sequence reaches its maximum value, it generates its minimum value. After a descending sequence reaches its minimum, it generates its maximum. NO CYCLE specifies that the sequence cannot generate more values after reaching its maximum or minimum value.

. How to access the current value and next value from a sequence? Is it possible to access the current value in a session before accessing next value

2009-03-04T03:29:00.000-08:00

Question :How to access the current value and next value from a sequence? Is it possible to access the current value in a session before accessing next value?
Answer :Sequence name CURRVAL, sequence name NEXTVAL. It is not possible. Only if you access next value in the session, current value can be accessed.

What is a database link

2009-03-04T03:28:00.000-08:00

Question :What is a database link?
Answer :Database link is a named path through which a remote database can be accessed.

If unique key constraint on DATE column is created, will it validate the rows that are inserted with SYSDATE

2009-03-04T03:27:00.001-08:00

Question :If unique key constraint on DATE column is created, will it validate the rows that are inserted with SYSDATE?
Answer :It won't, Because SYSDATE format contains time attached with it.

How will you activate/deactivate integrity constraints

2009-03-04T03:23:00.000-08:00

Question :How will you activate/deactivate integrity constraints?
Answer :The integrity constraints can be enabled or disabled by ALTER TABLE ENABLE CONSTRAINT / DISABLE CONSTRAINT.

Where the integrity constraints are stored in data dictionary

2009-03-04T03:21:00.000-08:00

Question :Where the integrity constraints are stored in data dictionary?
Answer :The integrity constraints are stored in USER_CONSTRAINTS.

What are the pre-requisites to modify datatype of a column and to add a column with NOT NULL constraint

2009-03-04T03:20:00.000-08:00

Question :What are the pre-requisites to modify datatype of a column and to add a column with NOT NULL constraint?
Answer :- To modify the datatype of a column the column must be empty. - To add a column with NOT NULL constrain, the table must be empty.

How many LONG columns are allowed in a table? Is it possible to use LONG columns in WHERE clause or ORDER BY

2009-03-04T03:11:00.000-08:00

Question :How many LONG columns are allowed in a table? Is it possible to use LONG columns in WHERE clause or ORDER BY?
Answer :Only one LONG column is allowed. It is not possible to use LONG column in WHERE or ORDER BY clause.

What is difference between CHAR and VARCHAR2? What is the maximum SIZE allowed for each type

2009-03-04T03:10:00.000-08:00

Question :What is difference between CHAR and VARCHAR2? What is the maximum SIZE allowed for each type?
Answer :CHAR pads blank spaces to the maximum length. VARCHAR2 does not pad blank spaces. For CHAR the maximum length is 255 and 2000 for VARCHAR2.

What are the data types allowed in a table

2009-03-04T03:09:00.000-08:00

Question :What are the data types allowed in a table?
Answer :CHAR, VARCHAR2, NUMBER, DATE, RAW, LONG and LONG RAW.

What is ON DELETE CASCADE

2009-03-04T03:07:00.000-08:00

Question :What is ON DELETE CASCADE?
Answer :When ON DELETE CASCADE is specified Oracle maintains referential integrity by automatically removing dependent foreign key values if a referenced primary or unique key value is removed.

What is the usage of SAVEPOINTS

2009-03-04T02:02:00.001-08:00

Question :What is the usage of SAVEPOINTS?
Answer :SAVEPOINTS are used to subdivide a transaction into smaller parts. It enables rolling back part of a transaction. Maximum of five save points are allowed.

What is referential integrity constraint

2009-03-04T02:02:00.000-08:00

Question :What is referential integrity constraint?
Answer :Maintaining data integrity through a set of rules that restrict the values of one or more columns of the tables based on the values of primary key or unique key of the referenced table.

What is an integrity constraint

2009-03-04T02:01:00.000-08:00

Question :What is an integrity constraint?
Answer :Integrity constraint is a rule that restricts values to a column in a table.

What is the fastest way of accessing a row in a table

2009-03-04T02:00:00.000-08:00

Question :What is the fastest way of accessing a row in a table?
Answer :Using ROWID.
CONSTRAINTS

What is ROWID

2009-03-04T01:58:00.000-08:00

Question :What is ROWID?
Answer :ROWID is a pseudo column attached to each row of a table. It is 18 characters long, blockno, rownumber are the components of ROWID.

Explain UNION, MINUS, UNION ALL and INTERSECT

2009-03-04T01:56:00.000-08:00

Question :Explain UNION, MINUS, UNION ALL and INTERSECT?
Answer :INTERSECT - returns all distinct rows selected by both queries. MINUS - returns all distinct rows selected by the first query but not by the second. UNION - returns all distinct rows selected by either query UNION ALL - returns all rows selected by either query, including all duplicates.

Difference between SUBSTR and INSTR

2009-03-04T01:55:00.000-08:00

Question :Difference between SUBSTR and INSTR?
Answer :INSTR (String1, String2 (n, (m)), INSTR returns the position of the m-th occurrence of the string 2 in string1. The search begins from nth position of string1. SUBSTR (String1 n, m) SUBSTR returns a character string of size m in string1, starting from n-th position of string1.

Explain CONNECT BY PRIOR

2009-03-04T01:53:00.000-08:00

Question :Explain CONNECT BY PRIOR?
Answer :Retrieves rows in hierarchical order eg. select empno, ename from emp where.

What is correlated sub-query

2009-03-04T01:50:00.000-08:00

Question :What is correlated sub-query?
Answer :Correlated sub-query is a sub-query, which has reference to the main query.

What is the sub-query

2009-03-04T01:49:00.000-08:00

Question :What is the sub-query?
Answer :Sub-query is a query whose return values are used in filtering conditions of the main query.

What is a join Explain the different types of joins

2009-03-04T01:48:00.000-08:00

Question :What is a join? Explain the different types of joins?
Answer :Join is a query, which retrieves related columns or rows from multiple tables. Self Join - Joining the table with itself. Equi Join - Joining two tables by equating two common columns. Non-Equi Join - Joining two tables by equating two common columns. Outer Join - Joining two tables in such a way that query can also retrieve rows that do not have corresponding join value in the other table.

What is difference between TRUNCATE & DELETE

2009-03-04T01:45:00.002-08:00

Question :What is difference between TRUNCATE & DELETE?
Answer :TRUNCATE commits after deleting entire table i.e., cannot be rolled back. Database triggers do not fire on TRUNCATE DELETE allows the filtered deletion. Deleted records can be rolled back or committed. Database triggers fire on DELETE.

What is a transaction

2009-03-04T01:45:00.001-08:00

Question :What is a transaction?
Answer :Transaction is logical unit between two commits and commit and rollback.

What are the dictionary tables used to monitor a database space

2009-03-04T01:41:00.000-08:00

Question :What are the dictionary tables used to monitor a database space?
Answer :DBA_FREE_SPACE DBA_SEGMENTS DBA_DATA_FILES.

What are the types of SQL statement

2009-03-04T01:39:00.000-08:00

Question :What are the types of SQL statement?
Answer :Data Definition Language: CREATE, ALTER, DROP, TRUNCATE, REVOKE, NO AUDIT & COMMIT. Data Manipulation Language: INSERT, UPDATE, DELETE, LOCK TABLE, EXPLAIN PLAN & SELECT. Transactional Control: COMMIT & ROLLBACK Session Control: ALTERSESSION & SET ROLE System Control: ALTER SYSTEM.

How will you enforce security using stored procedures

2009-03-04T01:36:00.000-08:00

Question :How will you enforce security using stored procedures?
Answer :Don't grant user access directly to tables within the application.Instead grant the ability to access the procedures that access the tables.When procedure executed it will execute the privilege of procedures owner. Users cannot access tables except via the procedure.

What is user Account in Oracle database

2009-03-04T01:35:00.000-08:00

Question :What is user Account in Oracle database?
Answer :A user account is not a physical structure in database but it is having important relationship to the objects in the database and will be having certain privileges.

List the factors that can affect the accuracy of the estimations

2009-03-04T01:34:00.000-08:00

Question :List the factors that can affect the accuracy of the estimations?
Answer :- The space used transaction entries and deleted records, does not become free immediately after completion due to delayed cleanout. - Trailing nulls and length bytes are not stored. - Inserts of, updates to and deletes of rows as well as columns larger than a single data block, can cause fragmentation a chained row pieces.

What are disadvantages of having raw devices

2009-03-04T01:33:00.000-08:00

Question :What are disadvantages of having raw devices?
Answer :We should depend on export/import utility for backup/recovery (fully reliable).The tar command cannot be used for physical file backup, instead we can use dd command, which is less flexible and has limited recoveries.

When will be a segment released

2009-03-04T01:32:00.000-08:00

Question :When will be a segment released?
Answer :When Segment is dropped. When Shrink (RBS only) When truncated (TRUNCATE used with drop storage option)

What is hit ratio

2009-03-04T01:30:00.000-08:00

Question :What is hit ratio?
Answer :It is a measure of well the data cache buffer is handling requests for data. Hit Ratio = (Logical Reads - Physical Reads - Hits Misses)/ Logical Reads.

What is a rollback segment entry

2009-03-04T01:29:00.000-08:00

Question :What is a rollback segment entry?
Answer :It is the set of before image data blocks that contain rows that are modified by a transaction. Each rollback segment entry must be completed within one rollback segment.A single rollback segment can have multiple rollback segment entries.

What is use of rollback segments in Oracle database

2009-03-04T01:28:00.002-08:00

Question :What is use of rollback segments in Oracle database?
Answer :They allow the database to maintain read consistency between multiple transactions.

What is advantage of having disk shadowing / mirroring

2009-03-04T01:28:00.001-08:00

Question :What is advantage of having disk shadowing / mirroring?
Answer :Shadow set of disks save as a backup in the event of disk failure. In most operating systems if any disk failure occurs it automatically switchover to place of failed disk.Improved performance because most OS support volume shadowing can direct file I/O request to use the shadow set of files instead of the main set of files. This reduces I/O load on the main set of disks.

What is redo log file mirroring How can be achieved

2009-03-04T01:27:00.001-08:00

Question :What is redo log file mirroring? How can be achieved?
Answer :Process of having a copy of redo log files is called mirroring.This can be achieved by creating group of log files together, so that LGWR will automatically writes them to all the members of the current on-line redo log group. If any one group fails then database automatically switch over to next group. It degrades performance.

How to implement the multiple control files for an existing database

2009-03-04T01:26:00.001-08:00

Question :How to implement the multiple control files for an existing database?
Answer :Shutdown the database Copy one of the existing controlfile to new location Edit Config ora file by adding new control filename Restart the database.

What is a Control file

2009-03-04T01:25:00.000-08:00

Question :What is a Control file?
Answer :Database's overall physical architecture is maintained in a file called control file. It will be used to maintain internal consistency and guide recovery operations. Multiple copies of control files are advisable.

It is possible to use raw devices as data files and what are the advantages over file system files

2009-03-04T01:24:00.000-08:00

Question :It is possible to use raw devices as data files and what are the advantages over file system files?
Answer :Yes.The advantages over file system files are that I/O will be improved because Oracle is bye-passing the kernel which writing into disk. Disk corruption will be very less.

How will you estimate the space required by a non-clustered tables

2009-03-04T01:23:00.000-08:00

Question :How will you estimate the space required by a non-clustered tables?
Answer :Calculate the total header size Calculate the available data space per data block Calculate the combined column lengths of the average row Calculate the total average row size. Calculate the average number rows that can fit in a block Calculate the number of blocks and bytes required for the table. After arriving the calculation, add 10 % additional space to calculate the initial extent size for a working table.

How can we plan storage for very large tables

2009-03-04T01:21:00.000-08:00

Question :How can we plan storage for very large tables?
Answer :Limit the number of extents in the table Separate table from its indexes. Allocate sufficient temporary storage.

List the sequence of events when a large transaction that exceeds beyond its optimal value when an entry wraps and causes the rollback segment to expa

2009-03-04T01:20:00.000-08:00

Question :List the sequence of events when a large transaction that exceeds beyond its optimal value when an entry wraps and causes the rollback segment to expand into another extend.
Answer :Transaction Begins. An entry is made in the RES header for new transactions entry Transaction acquires blocks in an extent of RBS The entry attempts to wrap into second extent. None is available, so that the RBS must extent. The RBS checks to see if it is part of its OPTIMAL size. RBS chooses its oldest inactive segment. Oldest inactive segment is eliminated. RBS extents The data dictionary tables for space management are updated. Transaction Completes.

How will you monitor rollback segment status

2009-03-04T01:18:00.000-08:00

Question :How will you monitor rollback segment status?
Answer :Querying the DBA_ROLLBACK_SEGS view IN USE - Rollback Segment is on-line. AVAILABLE - Rollback Segment available but not on-line. OFF-LINE - Rollback Segment off-line INVALID - Rollback Segment Dropped. NEEDS RECOVERY - Contains data but need recovery or corrupted. PARTLY AVAILABLE - Contains data from an unresolved transaction involving a distributed database.

How will you monitor the space allocation

2009-03-04T01:09:00.000-08:00

Question :How will you monitor the space allocation?
Answer :By querying DBA_SEGMENT table/view

Why query fails sometimes

2009-03-04T01:07:00.002-08:00

Question :Why query fails sometimes?
Answer :Rollback segment dynamically extent to handle larger transactions entry loads.A single transaction may wipeout all available free space in the rollback segment tablespace. This prevents other user using rollback segments.

How the space utilization takes place within rollback segments

2009-03-04T01:07:00.001-08:00

Question :How the space utilization takes place within rollback segments?
Answer :It will try to fit the transaction in a cyclic fashion to all existing extents. Once it found an extent is in use then it forced to acquire a new extent (number of extents is based on the optimal size)

How will you create multiple rollback segments in a database

2009-03-04T01:06:00.001-08:00

Question :How will you create multiple rollback segments in a database?
Answer :- Create a database, which implicitly creates a SYSTEM rollback segment in a SYSTEM tablespace. - Create a second rollback segment name R0 in the SYSTEM tablespace. - Make new rollback segment available (after shutdown, modify init.ora file and start database) - Create other tablespaces (RBS) for rollback segments. - Deactivate rollback segment R0 and activate the newly created rollback segments.

What is the functionality of SYSTEM table space

2009-03-04T01:05:00.000-08:00

Question :What is the functionality of SYSTEM table space?
Answer :To manage the database level transactions such as modifications of the data dictionary table that record information about the free space usage.

What is the OPTIMAL parameter

2009-03-04T01:03:00.000-08:00

Question :What is the OPTIMAL parameter?
Answer :It is used to set the optimal length of a rollback segment.

What is the OPTIMAL parameter

2009-03-03T23:19:00.000-08:00

Question :What is the OPTIMAL parameter?
Answer :It is used to set the optimal length of a rollback segment.

What is the role of PCTFREE parameter is storage clause

2009-03-03T23:18:00.000-08:00

Question :What is the role of PCTFREE parameter is storage clause?
Answer :This is used to reserve certain amount of space in a block for expansion of rows.

How does Space allocation table place within a block

2009-03-03T23:17:00.000-08:00

Question :How does Space allocation table place within a block?
Answer :Each block contains entries as follows Fixed block header Variable block header Row Header, row date (multiple rows may exists) PCTEREE (% of free space for row updating in future)

What is the significance of having storage clause

2009-03-03T23:16:00.000-08:00

Question :What is the significance of having storage clause?
Answer :We can plan the storage for a table as how much initial extents are required, how much can be extended next, how much % should leave free for managing row updating, etc.,

Which parameter in Storage clause will reduce number of rows per block

2009-03-03T23:15:00.000-08:00

Question :Which parameter in Storage clause will reduce number of rows per block?
Answer :PCTFREE parameter
Row size also reduces no of rows per block.

What is meant by free extent

2009-03-03T23:14:00.000-08:00

Question :What is meant by free extent?
Answer :A free extent is a collection of continuous free blocks in tablespace. When a segment is dropped its extents are reallocated and are marked as free.

How will you force database to use particular rollback segment

2009-03-03T23:13:00.000-08:00

Question :How will you force database to use particular rollback segment?
Answer :SET TRANSACTION USE ROLLBACK SEGMENT rbs_name.
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List the Optional Flexible Architecture (OFA) of Oracle database How can we organize the tablespaces in Oracle database to have maximum performance

2009-03-03T23:12:00.000-08:00

Question :List the Optional Flexible Architecture (OFA) of Oracle database? How can we organize the tablespaces in Oracle database to have maximum performance?
Answer :Oracle database to have maximum performance? SYSTEM - Data dictionary tables. DATA - Standard operational tables. DATA2- Static tables used for standard operations INDEXES - Indexes for Standard operational tables. INDEXES1 - Indexes of static tables used for standard operations. TOOLS - Tools table. TOOLS1 - Indexes for tools table. RBS - Standard Operations Rollback Segments, RBS1,RBS2 - Additional/Special Rollback segments. TEMP - Temporary purpose tablespace TEMP_USER - Temporary tablespace for users. USERS - User tablespace.

How will you swap objects into a different table space for an existing database

2009-03-03T23:11:00.002-08:00

Question :How will you swap objects into a different table space for an existing database?
Answer :- Export the user - Perform import using the command imp system/manager file=export.dmp indexfile=newrite.sql. This will create all definitions into newfile.sql. - Drop necessary objects. - Run the script newfile.sql after altering the tablespaces. - Import from the backup for the necessary objects.

What is redo log buffer

2009-03-03T23:11:00.001-08:00

Question :What is redo log buffer?
Answer :Changes made to the records are written to the on-line redo log files. So that they can be used in roll forward operations during database recoveries. Before writing them into the redo log files, they will first brought to redo log buffers in SGA and LGWR will write into files frequently. LOG_BUFFER parameter will decide the size.

What is meant by recursive hints

2009-03-03T23:10:00.001-08:00

Question :What is meant by recursive hints?
Answer :Number of times processes repeatedly query the dictionary table is called recursive hints. It is due to the data dictionary cache is too small. By increasing the SHARED_POOL_SIZE parameter we can optimize the size of data dictionary cache.

What is meant by recursive hints

2009-03-03T23:10:00.000-08:00

What is dictionary cache

2009-03-03T23:09:00.000-08:00

Question :What is dictionary cache?
Answer :Dictionary cache is information about the database objects stored in a data dictionary table.

What is Database Buffers

2009-03-03T23:08:00.000-08:00

Question :What is Database Buffers?
Answer :Database buffers are cache in the SGA used to hold the data blocks that are read from the data segments in the database such as tables, indexes and clusters DB_BLOCK_BUFFERS parameter in INIT.ORA decides the size.

What are the factors causing the reparsing of SQL statements in SGA

2009-03-03T23:06:00.000-08:00

Question :What are the factors causing the reparsing of SQL statements in SGA?
Answer :Due to insufficient shared pool size.Monitor the ratio of the reloads takes place while executing SQL statements. If the ratio is greater than 1 then increase the SHARED_POOL_SIZE.

What is a data segment

2009-03-03T23:05:00.000-08:00

Question :What is a data segment?
Answer :Data segment are the physical areas within a database block in which the data associated with tables and clusters are stored.

What is mean by Program Global Area (PGA)

2009-03-03T23:04:00.000-08:00

Question :What is mean by Program Global Area (PGA)?
Answer :It is area in memory that is used by a single Oracle user process.

What is a shared pool

2009-03-03T23:03:00.000-08:00

Question :What is a shared pool?
Answer :The data dictionary cache is stored in an area in SGA called the shared pool. This will allow sharing of parsed SQL statements among concurrent users.

What is SGA

2009-03-03T23:02:00.000-08:00

Question :What is SGA?
Answer :The System Global Area in an Oracle database is the area in memory to facilitate the transfer of information between users. It holds the most recently requested structural information between users. It holds the most recently requested structural information about the database. The structure is database buffers, dictionary cache, redo log buffer and shared pool area.

What is a deadlock? Explain.

2009-03-03T23:01:00.000-08:00

Question :What is a deadlock? Explain.
Answer :Two processes waiting to update the rows of a table, which are locked by other processes then deadlock arises.In a database environment this will often happen because of not issuing the proper row lock commands. Poor design of front-end application may cause this situation and the performance of server will reduce drastically.These locks will be released automatically when a commit/rollback operation performed or any one of this processes being killed externally.

What are the basic element of base configuration of an Oracle database

2009-03-03T23:00:00.000-08:00

Question :What are the basic element of base configuration of an Oracle database?
Answer :It consists of one or more data files. one or more control files. two or more redo log files. The Database contains multiple users/schemas one or more rollback segments one or more tablespaces Data dictionary tables User objects (table,indexes,views etc.,) The server that access the database consists of SGA (Database buffer, Dictionary Cache Buffers, Redo log buffers, Shared SQL pool) SMON (System MONito) PMON (Process MONitor) LGWR (LoG Write) DBWR (Data Base Write) ARCH (ARCHiver) CKPT (Check Point) RECO Dispatcher User Process with associated PGS

What is a cluster key

2009-03-03T22:59:00.000-08:00

Question :What is a cluster key?
Answer :The related columns of the tables are called the cluster key. The cluster key is indexed using a cluster index and its value is stored only once for multiple tables in the cluster.

What are clusters

2009-03-03T22:58:00.000-08:00

Question :What are clusters?
Answer :Group of tables physically stored together because they share common columns and are often used together is called cluster.

What is an index How it is implemented in Oracle database

2009-03-03T22:57:00.000-08:00

Question :What is an index? How it is implemented in Oracle database?
Answer :An index is a database structure used by the server to have direct access of a row in a table. An index is automatically created when a unique of primary key constraint clause is specified in create table command

What is a schema

2009-03-03T22:56:00.000-08:00

Question :What is a schema?
Answer :The set of objects owned by user account is called the schema.

What is Parallel Server

2009-03-03T22:55:00.000-08:00

Question :What is Parallel Server?
Answer :Multiple instances accessing the same database (only in multi-CPU environments)

What is a database instance? Explain.

2009-03-03T22:54:00.000-08:00

Question :What is a database instance? Explain.
Answer :A database instance (Server) is a set of memory structure and background processes that access a set of database files. The processes can be shared by all of the users.The memory structure that is used to store the most queried data from database. This helps up to improve database performance by decreasing the amount of I/O performed against data file.

What is a deadlock? Explain.

2009-03-03T22:53:00.000-08:00

What are the basic element of base configuration of an Oracle database

2009-03-03T22:52:00.000-08:00

What is a cluster key

2009-03-03T22:51:00.000-08:00

What are clusters

2009-03-03T22:50:00.002-08:00

Question :What are clusters?
Answer :Group of tables physically stored together because they share common columns and are often used together is called cluster.

What is an index How it is implemented in Oracle database

2009-03-03T22:50:00.001-08:00

What is a schema

2009-03-03T22:48:00.000-08:00

Question :What is a schema?
Answer :The set of objects owned by user account is called the schema.

What is Parallel Server

2009-03-03T22:40:00.000-08:00

Question :What is Parallel Server?
Answer :Multiple instances accessing the same database (only in multi-CPU environments)

What is a database instance Explain.

2009-03-03T22:22:00.000-08:00

Question :What is a database instance ? Explain.
Answer :A database instance (Server) is a set of memory structure and background processes that access a set of database files. The processes can be shared by all of the users.The memory structure that is used to store the most queried data from database. This helps up to improve database performance by decreasing the amount of I/O performed against data file.

What is the use of control file

2009-03-03T05:49:00.002-08:00

Question :What is the use of control file?
Answer :When an instance of an Oracle database is started, its control file is used to identify the database and redo log files that must be opened for database operation to proceed. It is also used in database recovery.

What does a control file contains

2009-03-03T05:49:00.001-08:00

Question :What does a control file contains?
Answer :- Database name - Names and locations of a database's files and redolog files. - Time stamp of database creation.

What is the use of redo log information

2009-03-03T05:48:00.001-08:00

Question :What is the use of redo log information?
Answer :The information in a redo log file is used only to recover the database from a system or media failure prevents database data from being written to a database's data files.

What is the function of redo log

2009-03-03T05:47:00.000-08:00

Question :What is the function of redo log?
Answer :The primary function of the redo log is to record all changes made to data.

What is a redo log

2009-03-03T05:45:00.000-08:00

Question :What is a redo log?
Answer :The set of redo log files for a database is collectively known as the database redo log.

What are the characteristics of data files

2009-03-03T05:44:00.000-08:00

Question :What are the characteristics of data files?
Answer :A data file can be associated with only one database. Once created a data file can't change size. One or more data files form a logical unit of database storage called a tablespace.

What is a datafile

2009-03-03T05:42:00.000-08:00

Question :What is a datafile?
Answer :Every Oracle database has one or more physical data files. A database's data files contain all the database data. The data of logical database structures such as tables and indexes is physically stored in the data files allocated for a database.

What is a temporary segment

2009-03-03T05:41:00.000-08:00

Question :What is a temporary segment?
Answer :Temporary segments are created by Oracle when a SQL statement needs a temporary work area to complete execution. When the statement finishes execution, the temporary segment extents are released to the system for future use.

What are the uses of rollback segment

2009-03-03T05:39:00.000-08:00

Question :What are the uses of rollback segment?
Answer :To generate read-consistent database information during database recovery and to rollback uncommitted transactions by the users.

What is rollback segment

2009-03-03T05:38:00.000-08:00

Question :What is rollback segment?
Answer :A database contains one or more rollback segments to temporarily store "undo" information.

What is an index segment

2009-03-03T05:35:00.001-08:00

Question :What is an index segment?
Answer :Each index has an index segment that stores all of its data.
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What is an index segment

2009-03-03T05:35:00.000-08:00

What is a data segment

2009-03-03T05:33:00.000-08:00

Question :What is a data segment?
Answer :Each non-clustered table has a data segment. All of the table's data is stored in the extents of its data segment. Each cluster has a data segment. The data of every table in the cluster is stored in the cluster's data segment.