Oracle 7.3 Interview Questions & Answers

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Oracle 7.3 Interview Questions & Answers

Are you in search of Oracle 7.3 jobs? Then we have provided you with the complete details about the Oracle 7.3 Interview Questions and Answers on our site. To be precise about the Oracle 7.3 Oracle Database (usually stated to as Oracle RDBMS or basically as Oracle) is a multi-model database management system formed and promoted by Oracle Corporation. It is the world's greatest common database for running online transaction processing (OLTP), data warehousing (DW) and mixed (OLTP & DW) database workloads. If you are Good at Oracle then there are various companies that offer jobs in various position like QA Analyst 3-ProdDev, Applications Developer, Oracle Knowledge Management, IT Database Analyst (Oracle, SQL Server) and many other roles too. To know more about Oracle 7.3, visit our site www.wisdomjobs.com.

Oracle 7.3 Interview Questions

Oracle 7.3 Interview Questions
    1. Question 1. Explain Oracle Datatypes?

      Answer :

      The Oracle datatypes :

      1. CHAR
      2. VARCHAR2
      3. VARCHAR
      4. NUMBER
      5. DATE
      6. LONG
      7. RAW
      8. LONG RAW.
      9. ROWID
      10. MLSLABEL.

    2. Question 2. How Rowids Are Used?

      Answer :

      Oracle uses ROWIDs internally for the construction of indexes. Each key in an index is associated with a ROWID that points to the associated row’s address for fast access.End–users and application developers can also use ROWIDs for several important uses:

      • ROWIDs are the fastest means of accessing particular rows.
      • ROWIDs can be used to see how a table is organized.
      • ROWIDs are unique identifiers for rows in a given table.

    3. Question 3. Explain About Data Conversions In Oracle 7.3?

      Answer :

      In some cases, Oracle supplies data of one datatype where it expects data of a different datatype. This is allowed when Oracle can automatically convert the data to the expected datatype using one of the following functions:

      • TO_NUMBER()
      • TO_CHAR()
      • TO_DATE()
      • TO_LABEL()
      • CHARTOROWID()
      • ROWIDTOCHAR()
      • HEXTOCHAR()
      • CHARTOHEX()

    4. Question 4. Explain Hash Functions In Oracle 7.3?

      Answer :

      A hash function is a function applied to a cluster key value that returns a hash value. Oracle then uses the hash value to locate the row in the proper data block of the hash cluster. The job of a hash function is to provide the maximum distribution of rows among the available hash values of the cluster. To achieve this goal, a hash function must minimize the number of collisions.

       

    5. Question 5. Why Cluster Key Used?

      Answer :

      The cluster key is the column, or group of columns, that the clustered tables have in common. You specify the columns of the cluster key when creating the cluster. You subsequently specify the same columns when creating every table added to the cluster.

    6. Question 6. Explain About Clusters?

      Answer :

      Clusters are an optional method of storing table data. A cluster is a group of tables that share the same data blocks because they share common columns and are often used together. For example, the EMP and DEPT table share the DEPTNO column. When you cluster the EMP and DEPT tables , Oracle physically stores all rows for each department from both the EMP and DEPT tables in the same data blocks.

    7. Question 7. Explain About Unique And Non–unique Indexes In Oracle 7.3?

      Answer :

      Indexes can be unique or non–unique. Unique indexes guarantee that no two rows of a table have duplicate values in the columns that define the index. Non–unique indexes do not impose this restriction on the column values.

      Oracle recommends that you do not explicitly define unique indexes on tables; uniqueness is strictly a logical concept and should be associated with the definition of a table. Alternatively, define UNIQUE integrity constraints on the desired columns. Oracle enforces UNIQUE integrity constraints by automatically defining a unique index on the unique key

    8. Question 8. Explain About Composite Indexes?

      Answer :

      A composite index (also called a concatenated index) is an index that you create on multiple columns in a table. Columns in a composite index can appear in any order and need not be adjacent in the table. Composite  indexes can speed retrieval of data for SELECT statements in which the WHERE clause references all or the leading portion of the columns in the composite index. Therefore, you should give some thought to the order of the columns used in the definition; generally, the most commonly accessed or most selective columns go first.

    9. Question 9. What Is The Use Of The Sequence Generator In Oracle?

      Answer :

      The sequence generator provides a sequential series of numbers. The sequence generator is especially useful in multi–user environments for generating unique sequential numbers without the overhead of disk I/O or transaction locking. Therefore, the sequence generator reduces “serialization” where the statements of two transactions must generate sequential numbers at the same time. By avoiding the serialization that results when multiple users wait for each other to generate and use a sequence number, the sequence generator improves transaction throughput and a user’s wait is considerably shorter.

    10. Question 10. Explain The Rules For Updatable Join Views?

      Answer :

      1. General Rule  Any INSERT, UPDATE, or DELETE operation on a join view can modify only one underlying base table at a time.
      2. UPDATE Rule All updatable columns of a join view must map to columns of a key preserved table. If the view is defined with the WITH CHECK OPTION clause, then all join columns and all columns of repeated tables are non–updatable.
      3. DELETE Rule Rows from a join view can be deleted as long as there is exactly one key–preserved table in the join. If the view is defined with the WITH CHECK OPTION clause and the key preserved table is repeated, then the rows cannot be deleted from the view.
      4. INSERT Rule An INSERT statement must not, explicitly or implicitly, refer to the columns of a non–key preserved table. If the join view is defined with the WITH CHECK OPTION clause, then INSERT statements are not permitted.

    11. Question 11. What Is A Null?

      Answer :

      A null is the absence of a value in a column of a row. Nulls indicate missing, unknown, or inapplicable data. A null should not be used to imply any other value, such as zero. A column allows nulls unless a NOT NULL or PRIMARY KEY integrity constraint has been defined for the column, in which case no row can be inserted without a value for that column.

    12. Question 12. What Is A Datafile?

      Answer :

      Each tablespace in an Oracle database is comprised of one or more operating system files called datafiles. A tablespace’s datafiles physically store the associated database data on disk.

    13. Question 13. What Is A Table Space?

      Answer :

      An Oracle database is comprised of one or more logical storage units called tablespaces. The database’s data is collectively stored in the database’s tablespaces. A database administrator can use tablespaces to do the following:

      • control disk space allocation for database data.
      • assign specific space quotas for database users.
      • control availability of data by taking individual tablespaces online or offline.
      • perform partial database backup or recovery operations.
      • allocate data storage across devices to improve performance.

    14. Question 14. What Are The Operations Required In Temporary Segments?

      Answer :

      The following commands may require the use of a temporary segment:

      • CREATE INDEX
      • SELECT ... ORDER BY
      • SELECT DISTINCT ...
      • SELECT ... GROUP BY
      • SELECT ... UNION
      • SELECT ... INTERSECT
      • SELECT ... MINUS
      • unindexed joins
      • certain correlated subqueries

    15. Question 15. Explain About Temporary Segments?

      Answer :

      Temporary Segments : When processing queries, Oracle often requires temporary workspace for intermediate stages of SQL statement processing. Oracle automatically allocates this disk space called a temporary segment.Typically, Oracle requires a temporary segment as a work area for sorting. Oracle does not create a segment if the sorting operation can be done in memory or if Oracle finds some other way to perform the operation using indexes.

    16. Question 16. Explain About Segments? Types Of Segments?

      Answer :

      Segments : A segment is a set of extents that contain all the data for a specific logical storage structure within a tablespace. For example, for each table, Oracle allocates one or more extents to form that table’s data segment, and, for each index, Oracle allocates one or more extents to form its index segment.

      There are four types of segments used in Oracle databases:

      1. data segments.
      2. index segments.
      3. rollback segments.
      4. temporary segments.

    17. Question 17. What Are Data Blocks?

      Answer :

      Data Blocks : Oracle manages the storage space in the datafiles of a database in units called data blocks. A data block is the smallest unit of I/O used by a database. 

    18. Question 18. What Are Parameter Files?

      Answer :

      Parameter Files : To start an instance, Oracle must read a parameter file.A parameter file is a text file containing a list of instance configuration parameters. You set these parameters to particular values and to initialize many of the memory and process settings of an Oracle instance. Among other things, the parameters of this file tell Oracle the following:

      • the name of the database for which to start up an instance.
      • how much memory to use for memory structures in the SGA.
      • what to do with filled online redo log files.
      • the names and locations of the database’s control files.
      • the names of private rollback segments in the database.

    19. Question 19. What Are The Database And Instance Shut Down Steps?

      Answer :

      There are three steps to shutting down an instance and the database to which it is connected:

      • Close the database.
      • Dismount the database.
      • Shut down the instance.

      Oracle automatically performs all three steps when an instance is shut down.

    20. Question 20. What Are The Steps For Database And Instance Startup?

      Answer :

      There are three steps to starting a database and making it available for systemwide use:

      • Start an instance.
      • Mount the database.
      • Open the database.

    21. Question 21. Explain About The Security Mechanisms In Oracle 7.3?

      Answer :

      Security Mechanisms  : The Oracle Server provides discretionary access control, which is a means of restricting access to information based on privileges. The appropriate privilege must be assigned to a user in order for that user to access an object. Appropriately privileged users can grant other users privileges at their discretion; for this reason, this type of security is called “discretionary”.

      Oracle manages database security using several different facilities:

      • database users and schemas
      • privileges
      • roles
      • storage settings and quotas
      • resource limits
      • auditing

    22. Question 22. What Are The Integrity Constraints In Oracle?

      Answer :

      An integrity constraint is a declarative way to define a business rule for a column of a table. An integrity constraint is a statement about a table’s data that is always true:

      • If an integrity constraint is created for a table and some existing table data does not satisfy the constraint, the constraint cannot be enforced.
      • After a constraint is defined, if any of the results of a DML statement violate the integrity constraint, the statement is rolled back and an error is returned.

      Integrity constraints are defined with a table and are stored as part of the table’s definition, centrally in the database’s data dictionary, so that all database applications must adhere to the same set of rules. If a rule changes, it need only be changed once at the database level and not many times for each application.

      The following integrity constraints are supported by Oracle:

      • Disallows nulls (empty entries) in a table’s column.
      • Disallows duplicate values in a column or set of columns.
      • Disallows duplicate values and nulls in a column or set of columns.
      • Requires each value in a column or set of columns match a value in a related table’s UNIQUE or PRIMARY KEY (FOREIGN KEY integrity constraints also define referential integrity actions that dictate what Oracle should do with dependent data if the data it references is altered).
      • Disallows values that do not satisfy the logical expression of the constraint.

    23. Question 23. Explain About The Program Interface?

      Answer :

      The Program Interface : The program interface is the mechanism by which a user process communicates with a server process. It serves as a method of standard communication between any client tool or application (such as Oracle Forms) and Oracle software. 

    24. Question 24. What Is Pmon?

      Answer :

      Process Monitor (PMON) The process monitor performs process recovery when a user process fails. PMON is responsible for cleaning up the cache and freeing resources that the process was using. PMON also checks on dispatcher (see below) and server processes and restarts them if they have failed.

    25. Question 25. What Is System Monitor (smon)?

      Answer :

      System Monitor (SMON) The system monitor performs instance recovery at instance startup. In a multiple instance system (one that uses the Parallel Server), SMON of one instance can also perform instance recovery for other instances that have failed.

      SMON also cleans up temporary segments that are no longer in use and recovers dead transactions skipped during crash and instance recovery because of file–read or offline errors.

      These transactions are eventually recovered by SMON when the tablespace or file is brought back online. SMON also coalesces free extents within the database to make free space contiguous and easier to allocate.

    26. Question 26. What Is Checkpoint?

      Answer :

      Checkpoint (CKPT) At specific times, all modified database buffers in the system global area are written to the datafiles by DBWR; this event is called a checkpoint. The Checkpoint process is responsible for signalling DBWR at checkpoints and updating all the datafiles and control files of the database to indicate the most recent checkpoint. CKPT is optional; if CKPT is not present, LGWR assumes the responsibilities of CKPT.

    27. Question 27. What Is A Log Writer (lgwr)?

      Answer :

      Log Writer (LGWR) The Log Writer writes redo log entries to disk. Redo log data is generated in the redo log buffer of the system global area. As transactions commit and the log buffer fills, LGWR writes redo log entries into an online redo log file.

    28. Question 28. What Is A Processes?

      Answer :

      Processes : A process is a “thread of control” or a mechanism in an operating system that can execute a series of steps. Some operating systems use the terms job or task. A process normally has its own private memory area in which it runs.

    29. Question 29. Explain About Oracle Data Blocks?

      Answer :

      At the finest level of granularity, an Oracle database’s data is stored in data blocks. One data block corresponds to a specific number of bytes of physical database space on disk. A data block size is specified for each Oracle database when the database is created. A database uses and allocates free database space in Oracle data blocks.

       

    30. Question 30. What Is Database Enforced Integrity?

      Answer :

      database enforced integrity :  Oracle enforces data integrity, “business rules” that dictate the standards for acceptable data. As a result, the costs of coding and managing checks in many database applications are eliminated.

    31. Question 31. How Views Are Used?

      Answer :

      Views provide a means to present a different representation of the data that resides within the base tables. Views are very powerful because they allow you to tailor the presentation of data to different types of users. Views are often used

      • to provide an additional level of table security by restricting access to a predetermined set of rows and/or columns of a table
      • to hide data complexity.
      • to simplify commands for the user.
      • to present the data in a different perspective from that of the base table.
      • to hide data complexity.
      • to simplify commands for the user.
      • to present the data in a different perspective from that of the base table.
      • to isolate applications from changes in definitions of base tables.
      • to express a query that cannot be expressed without using a view.
      • to save complex queries.
      • to achieve improvements in availability and performance.

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