ORACLE DBA INTERVIEW QUESTIONS AND ANSWERS
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81. Give the reasoning behind using an index.
Faster access to data blocks in a table
82. What command would you use to create a backup control file?
Alter database backup control file to trace
83. How do you set up tablespaces during an Oracle installation?
You should always attempt to use the Oracle Flexible Architecture standard or another partitioning scheme to ensure proper separation of SYSTEM, ROLLBACK, REDO LOG, DATA, TEMPORARY and INDEX segments
84. Discuss row chaining, how does it happen? How can you reduce it? How do you correct it
Row chaining occurs when a VARCHAR2 value is updated and the length of the new value is longer than the old value and won?t fit in the remaining block space. This results in the row chaining to another block. It can be reduced by setting the storage parameters on the table to appropriate values. It can be corrected by export and import of the effected table.
85. How can you find out how many users are currently logged into the database? How can you find their operating system id
There are several ways. One is to look at the v$session or v$process views. Another way is to check the current_logins parameter in the v$sysstat view. Another if you are on UNIX is to do a "ps -ef|grep oracle|wc -l? command, but this only works against a single instance installation.
86. What is a Cartesian product
A Cartesian product is the result of an unrestricted join of two or more tables. The result set of a three table Cartesian product will have x * y * z number of rows where x, y, z correspond to the number of rows in each table involved in the join
87. How do you generate file output from SQL
By use of the SPOOL comm
88.Which datatype is used for storing graphics and images
LONG RAW data type is used for storing BLOB's (binary large objects).
89. How should a many-to-many relationship be handled
By adding an intersection entity table
90. Define OFA.
OFA stands for Optimal Flexible Architecture. It is a method of placing directories and files in an Oracle system so that you get the maximum flexibility for future tuning and file placement
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