zoukankan      html  css  js  c++  java
  • 052-193(新增70题2018)

    Users complain about the slow response time of queries. While investigating the cause you find that the Oracle Instance is not configured to cache all of the data blocks to satisfy the user's queries.
    Which component of the Oracle Instance would you change to improve performance?
    A. Java pool
    B. Large pool
    C. Shared pool
    D. Streams pool
    E. Library cache
    F. Redo log buffer
    G. Data dictionary cache
    H. Database buffer cache
    Answer: H

    应该是database buffer cache不够导致缓存命中率低下要产生新的IO导致查询时间增长。

    Database Buffer Cache

    Oracle Database uses the buffer cache to achieve the following goals:

    • Optimize physical I/O

      The database updates data blocks in the cache and stores metadata about the changes in the redo log buffer. After a COMMIT, the database writes the redo buffers to disk but does not immediately write data blocks to disk. Instead, database writer (DBW) performs lazy writes in the background.

    • Keep frequently accessed blocks in the buffer cache and write infrequently accessed blocks to disk

      When Database Smart Flash Cache (flash cache) is enabled, part of the buffer cache can reside in the flash cache. This buffer cache extension is stored on a flash disk device, which is a solid state storage device that uses flash memory. The database can improve performance by caching buffers in flash memory instead of reading from magnetic disk.




  • 相关阅读:
    循环结构
    位运算符
    Switch 选择结构
    if结构和逻辑运算符
    变量和运算符
    [luogu1090 SCOI2003] 字符串折叠(区间DP+hash)
    [luogu2329 SCOI2005] 栅栏(二分+搜索)
    [luogu 4886] 快递员
    [luogu4290 HAOI2008]玩具取名(DP)
    [luogu2624 HNOI2008]明明的烦恼 (prufer+高精)
  • 原文地址:https://www.cnblogs.com/Babylon/p/8579772.html
Copyright © 2011-2022 走看看