shared pool_使用large pool

Using the Large Pool
使用large Pool

Unlike the shared pool, the large pool does not have an LRU list. Oracle does not
attempt to age objects out of the large pool.
不像shared pool，large pool不含有LRU 列表。ORACLE 不會嘗試把對象
因長期不用而從large pool中去除.
You should consider configuring a large pool if your instance uses any of the
following:

如果你的執行個體使用下面的任何一個，你應該考慮使用large pool：

■ Parallel query
Parallel query uses shared pool memory to cache parallel execution message
buffers.
並行查詢：
並行查詢將使用shared pool記憶體來把並存執行訊息緩衝起來
■ Recovery Manager
Recovery Manager uses the shared pool to cache I/O buffers during backup and
restore operations. For I/O server processes and backup and restore operations,
Oracle allocates buffers that are a few hundred kilobytes in size.

恢複管理
recover manager 使用shared pool來緩衝備份和恢複過程中 I/O buffer 裡面的資料。
針對I/O 服務進程，以及備份和恢複操作。Oracle將分配buffers ,大小有幾百K 。
■ Shared server
In a shared server architecture, the session memory for each client process is
included in the shared pool.

共用伺服器：
在共用伺服器訪問模式下，每個用戶端進程的會話記憶體都包含在共用池中。

Tuning the Large Pool and Shared Pool for the Shared Server Architecture
在共用伺服器模式下調試large pool和share pool

As Oracle allocates shared pool memory for shared server session memory, the
amount of shared pool memory available for the library cache and dictionary cache
decreases. If you allocate this session memory from a different pool, then Oracle can
use the shared pool primarily for caching shared SQL and not incur the performance
overhead from shrinking the shared SQL cache.

由於ORACLE 從share pool 記憶體中分配共用的會話記憶體，那就沒有足夠的 library cache
以及dictionary cache 供shared pool使用。如果你從不同的池裡為會話記憶體配置資料。
那麼ORACLE就可以使用share pool來緩衝共用SQL，從而不因為減少共用的SQL CACHE
影響效能。

Oracle recommends using the large pool to allocate the shared server-related User
Global Area (UGA), rather that using the shared pool.

Oracle 建議使用large pool來分配和共用伺服器相關的 UGA，而不是使用shared pool。

 This is because Oracle uses the shared pool to allocate System Global Area (SGA) memory for other purposes,
such as shared SQL and PL/SQL procedures. Using the large pool instead of the shared pool
decreases fragmentation of the shared pool.

這是因為為了其他原因 ORACLE將使用 shared pool來分配SGA 記憶體，比如共用SQL 以及PL/SQL預存程序。
使用large pool 而不是shared pool將減小shared pool的片段。