Performance Engineering Interview Question 8

Performance Engineering Interview Questions #8

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Following are the Performance Engineering Interview Questions Set #8.

Q. 36 What are the Oracle Database memory caches that affect performance?

Ans: The main Oracle Database memory caches that affect performance include:

  • Database Buffer Cache
  • Redo Log Buffer
  • Shared Pool
  • Large Pool
  • Java Pool
  • Streams Pool
  • Process-Private Memory
  • In-Memory Column Store

Q. 37 What is Database Buffer Cache?

The database buffer cache is the memory area that stores copies of data blocks read from data files. It is also called ‘buffer cache’. All users concurrently connected to a database instance share access to the buffer cache.

Purpose of the Database Buffer Cache:

  • Optimize physical I/O
  • Keep frequently accessed blocks in the buffer cache and write infrequently accessed blocks to disk

Q. 38 What is Redo Log Buffer?

Ans: The redo log buffer is a circular buffer in the SGA that stores redo entries describing changes made to the database.

A redo record is a data structure that contains the information necessary to reconstruct or redo, changes made to the database by DML or DDL operations. Database recovery applies redo entries to data files to reconstruct lost changes.

Q. 39 What is a Large Pool in Oracle DB?

Ans: The large pool is an optional memory area intended for memory allocations that are larger than is appropriate for the shared pool.

The large pool can provide large memory allocations for the following:

  • UGA for the shared server and the Oracle XA interface (used where transactions interact with multiple databases)
  • Message buffers used in parallel execution
  • Buffers for Recovery Manager (RMAN) I/O slaves
  • Buffers for deferred inserts (inserts with the MEMOPTIMIZE_WRITE hint)

Q. 40 What is a Shared Pool in Oracle DB?

Ans: The shared pool stores parsed SQL, PL/SQL code, system parameters, and data dictionary information. The shared pool is involved in almost every operation that occurs in the database. For example, if a user executes a SQL statement, then Oracle Database accesses the shared pool.

The shared pool is divided into several subcomponents,

  • Library Cache
  • Data Dictionary Cache
  • Server Result Cache
  • Reserved Pool

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