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DataBase Administrator (DBA) Interview Questions and Answers

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95. What UNIX command will control the default file permissions when files are created?

Umask


96. Explain the read, write, and execute permissions on a UNIX directory.

Read allows you to see and list the directory contents. Write allows you to create, edit and delete files and subdirectories in the directory. Execute gives you the previous read/write permissions plus allows you to change into the directory and execute programs or shells from the directory.


97. the difference between a soft link and a hard link?

A symbolic (soft) linked file and the targeted file can be located on the same or different file system while for a hard link they must be located on the same file system.


99. Give the command to display space usage on the UNIX file system.

df -lk


100. Explain iostat, vmstat and netstat.

Iostat reports on terminal, disk and tape I/O activity. Vmstat reports on virtual memory statistics for processes, disk, tape and CPU activity. Netstat reports on the contents of network data structures.


101. What is new_form built-in?

When one form invokes another form by executing new_form oracle form exits the first form and releases its memory before loading the new form calling new form completely replace the first with the second. If there are changes pending in the first form, the operator will be prompted to save them before the new form is loaded.


102. What is the “LOV of Validation” Property of an item? - What is the use of it?

When LOV for Validation is set to True, Oracle Forms compares the current value of the text item to the values in the first column displayed in the LOV. Whenever the validation event occurs. If the value in the text item matches one of the values in the first column of the LOV, validation succeeds, the LOV is not displayed, and processing continues normally. If the value in the text item does not match one of the values in the first column of the LOV, Oracle Forms displays the LOV and uses the text item value as the search criteria to automatically reduce the list.


103. What is the diff. when Flex mode is mode on and when it is off?

When flex mode is on, reports automatically resizes the parent when the child is resized.


104. What is ROWID?

Answer1
For each row in the database, the ROWID pseudocolumn returns a row’s address. ROWID values contain information necessary to locate a row:
* which data block in the data file
* which row in the data block (first row is 0)
* which data file (first file is 1)

Answer2
.row id: A rowid is a pseudo-column that uniquely identifies a row in a table, but not within a data base.


105. What is a correlated subquery?

A correlated subquery is a SELECT statement nested inside another T-SQL statement, which contains a reference to one or more columns in the outer query

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