What is a deadlock? Explain.

Two processes waiting to update the rows of a table, which are locked by other processes then deadlock arises.

In a database environment this will often happen because of not issuing the proper row lock commands. Poor design of front-end application may cause this situation and the performance of server will reduce drastically.

These locks will be released automatically when a commit/rollback operation performed or any one of this processes being killed externally

What is the basic element of base configuration of an Oracle database?

It consists of

one or more data files.

one or more control files.

two or more redo log files.

The Database contains

multiple users/schemas

one or more rollback segments

one or more tablespaces

Data dictionary tables

User objects (table,indexes,views etc.,)

The server that access the database consists of

SGA (Database buffer, Dictionary Cache Buffers, Redo log buffers, Shared SQL pool)

SMON (System MONito)

PMON (Process MONitor)

LGWR (LoG Write)

DBWR (Data Base Write)

ARCH (ARCHiver)

CKPT (Check Point)

RECO

Dispatcher

User Process with associated PGS

What is an extent?

An extent is a specific number of contiguous data blocks, obtained in a single allocation and used to store a specific type of information.

What is row chaining?

In circumstances, all of the data for a row in a table may not be able to fit in the same data block. When this occurs, the data for the row is stored in a chain of data block (one or more) reserved for that segment.

What is data block?

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.

What is public database link?

Public database link is created for the special user group PUBLIC. A public database link can be used when any user in the associated database specifies a global object name in a SQL statement or object definition.

What is private database link?

Private database link is created on behalf of a specific user. A private database link can be used only when the owner of the link specifies a global object name in a SQL statement or in the definition of the owner’s views or procedures.

What are the types of database links?

Private database link, public database link & network database link.

What is database link?

:A database link is a named object that describes a “path” from one database to another.

What is index cluster?

A cluster with an index on the cluster key.