Oracle体系结构及备份（九）——sga-large_pool

一 什么是Large Pool

 

        大池是系统全局区中可选的一个内存区。主要在下面几种情况中使用：共享服务器的全局用户区（UGA）、并行进程、使用RMAN作备份恢复。大小由参数LARGE_POOL_SIZE决定，也可以动态改变大小。

 

        The database administrator can configure an optional memory area called the large pool to provide large memory allocations for:

 

        Session memory for the shared server and the Oracle XA interface (used where transactions interact with more than one database)

 

        I/O server processes

 

        Oracle Database backup and restore operations

 

        By allocating session memory from the large pool for shared server, Oracle XA, or parallel query buffers, Oracle Database can use the shared pool primarily for caching shared SQL and avoid the performance
overhead caused by shrinking the shared SQL cache.

 

        In addition, the memory for Oracle Database backup and restore operations, for I/O server processes, and for parallel buffers is allocated in buffers of a few hundred kilobytes. The large pool is
better able to satisfy such large memory requests than the shared pool.

 

        The large pool does not have an LRU list. It is different from reserved space in the shared pool, which uses the same LRU list as other memory allocated from the shared pool.

 

 

二 操作示例

SQL> show parameter large_pool_size;

NAME				     TYPE	 VALUE
------------------------------------ ----------- ------------------------------
large_pool_size 		     big integer 0
--12M——14M足够
SQL> alter system set large_pool_size=10M;

System altered.

SQL> show parameter large_pool_size;

NAME				     TYPE	 VALUE
------------------------------------ ----------- ------------------------------
large_pool_size 		     big integer 12M

 

 

三 总结

 

        1.Large Pool：大池，是系统全局区中可选的一个内存区。

        2.可以通过参数large_pool_size查询大池的大小。

 

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By Larry Wen

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