Database-Oracle [3i Infotech Placement]: Sample Questions 10 - 10 of 132

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Question 10

Oracle
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Describe in Detail

Essay▾

What are the four Oracle system processes that must always be up and running for the database to be useable?

Explanation

  • The four Oracle system processes that must always be up and running for the database to be useable include:
  1. DBWR (Database Writer)
  2. LGWR (Long Writer)
  3. SMON (system Monitor)
  4. PMON (process Monitor) .

DBWR (database Writer)

Define Database Writer (DBWR) Process
  • Responsible for writing the actual data to physical database files at the operating system level.
  • Created at start of database instance.
  • Contents of dirty buffer to physical file is the responsibility of the DBWR process.

LGWR (Long Writer) :

Given Structure of Long Writer Process
  • Writes the contents of the redo log buffer to the log file on disk, and manages the log buffer
  • The LGWR writes the redo log buffers to the on-line redo log files.

SMON (system Monitor) :

Understanding of System Monitor
  • Most critical background process for Oracle Database.
  • Performs instance recovery, cleans up after dirty shutdowns and coalesces adjacent free extents into larger free extents.
  • Is always running for an instance. If not, the instance will terminate.

PMON (process Monitor) :

Understanding of Process Monitor Process
  • Process Monitor process recovers failed process resources.
  • Gets up every 3 seconds to perform its activities.
  • Is always running for an instance. If not, the instance will terminate.
  • Checks the status of dispatcher and server processes, and restarts any that have stopped running.
  • Registers information about the instance and dispatcher processes with the network listener.

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