Topic : Architecture

Explain types of large objects in oracle; i.e. BLOB; LLOB;NCLOB and BFILE.


Answer :

Internal LOBs:
BLOBs; CLOBs; and NCLOBs are Internal LOBs stored inside database tablespaces to optimize space and efficient access. Changes to internal LOBs can be committed or rolled back.
They use copy semantics and participate in the transactional model of the server and can be recovered on media failure.
The ACIDFoot 1 properties are applicable to internal LOBs too.
BLO
The BLOB data type stores binary large objects. BLOB can store up to 4 gigabytes of binary data.
CLOB
The CBLOB data type stores character large objects. CLOB can store up to 4 gigabytes of character data.
NCLOB
The NCBLOB data type stores character large objects in multibyte national character set. NCLOB can store up to 4 gigabytes of character data
External LOBs:
BFILES
BFILES are External LOBs stored in operating system files outside database tablespaces. These files use reference semantics.
The BFILE datatype allows read-only byte stream access to large files on the file system of the database server. The maximum file size supported is 4 gigabytes.

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Explain the steps executed during SQL statement processing.


Answer :

The parser scans the statement and breaks it into logical units such as keywords; identifiers and operators.
- A query or a sequence tree is built using the units above. This is done to transform the source data into the format required by the result set.
- The Query optimizer analyzes the fastest way to access the source tables using minimum resources. The final optimized version of the updated query tree is called as execution plan.
- Now; the relational engine starts to execute this plan. the relational engine requests that the storage engine pass up data from the row sets requested from the relational engine.
- In turn; the relational engine processes this data into the format as desired by result set and returns the same.

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How would you determine the time zone under which a database was operating?


Answer :

Select DBTIMEZONE from dual;

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Explain the use of setting GLOBAL_NAMES equal to TRUE.


Answer :

Setting GLOBAL_NAMES dictates how you might connect to a database. This variable is either TRUE or FALSE and if it is set to TRUE it enforces database links to have the same name as the remote database to which they are linking.

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What is a DBA?


Answer :

"A DBA is a Database Administrator; and this is the most common job that you find a database specialist doing. There are Development DBAs and Production DBAs.
A Development DBA usually works closely with a team of developers and gets more involved in design decisions; giving advice on performance and writing good SQL.
That can be satisfying at a human level because you are part of a team and you share the satisfaction of the teams accomplishments.
A Production DBA (on the other hand) is responsible for maintaining Databases within an organization; so it is a very difficult and demanding job. He or she; often gets involved when all the design decisions have been made; and has simply to keep things up and running.
Therefore; of course; it is also a rewarding job; both financially and in terms of job satisfaction. But it is a more ""lonely"" job than being a Development DBA."

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