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Cursors and SQL Areas (99)

原创 数据库开发技术 作者:tsinglee 时间:2007-10-25 11:28:37 0 删除 编辑

The application developer of an Oracle precompiler program or
OCI program can explicitly open cursors, or handles to specific private SQL areas, and
use them as a named resource throughout the execution of the program. Recursive
cursors that Oracle issues implicitly for some SQL statements also use shared SQL
areas.
The management of private SQL areas is the responsibility of the user process. The
allocation and deallocation of private SQL areas depends largely on which application
tool you are using, although the number of private SQL areas that a user process can
allocate is always limited by the initialization parameter OPEN_CURSORS. The default
value of this parameter is 50.
A private SQL area continues to exist until the corresponding cursor is closed or the
statement handle is freed. Although Oracle frees the runtime area after the statement
completes, the persistent area remains waiting. Application developers close all open
cursors that will not be used again to free the persistent area and to minimize the
amount of memory required for users of the application.

游标与SQL区
1. 用户进程可分配的最大私有SQL区受初始化参数OPEN_CURSORS的限制
2. 当相应的游标被关闭或者语句句柄被释放时, 私有SQL区才消失
3. runtime area在SQL语句结束后释放, persistent area则继续等待(什么?)

[@more@]

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