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DB Administration Interview Questions

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Character functions analyze and modify the contents of CHAR and VARCHAR2 string variables.
Numeric functions are a full range of operations that manipulate numbers, including trigonometric, logarithmic, and exponential functions.
Date functions are utilities that allow programmers to perform high-level actions on date variables, including date arithmetic.
Conversion functions convert from one datatype to another, often formatting the output data at the same time.
LOB functions allow operations on LOB (large object) data.
Miscellaneous functions perform operations that don't fall into any of the other categories.
Example of built in functions:
1. to_date - a convertion function that will convert a string date to a date datatype
2. sum - a group function that will return the summation of all values in the column
3. upper - a single row function that will return all characters in a column in upper case

Multiple instances accessing the same database (Only In Multi-CPU environments)

A synonym is an alternative name for objects such as tables, views, sequences, stored procedures, and other database objects.
A synonym (synonym-name) is an alias for an object (such as a table). The object does not need to exist at the time of its creation. Synonyms can't be used in a drop and truncate statements. If this is tried, it results in a ORA-00942: table or view does not exist
The syntax for creating a synonym is:
create [or replace] [public] synonym [schema .] synonym_name for [schema .] object_name [@ dblink];
The or replace phrase allows you to recreate the synonym (if it already exists) without having to issue a DROP synonym command.
The public phrase means that the synonym is a public synonym and is accessible to all users. Remember though that the user must first have the appropriate privileges to the object to use the synonym.
The schema phrase is the appropriate schema. If this phrase is omitted, Oracle assumes that you are referring to your own schema.
The object_name phrase is the name of the object for which you are creating the synonym. It can be one of the following:
table package
view materialized view
sequence java class schema object
stored procedure user-defined object
function synonym
Type of Synonym are:-
Public (Accessible to all)
Private (Accessible to owner)

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

Yes we can decrease the size of the datafile to the place where the extents are deallocated in to it by resizing the datafiles to something smaller than current. If the data in the datafile is scattered than reorg the object in the tablespace to deallocate the extent and decrease the filesize
We can reduce the size of the datafile till the high watermark of the datafile. IF we have to bring down the high watermark then we have to check the extents in the file and reorganize objects as required.

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