比较权威的流程图
SQL Parsing Flow Diagram
========================
Statement
Submitted
|
Is it in an open cursor?--------------YES----V
| |
NO |
| |
Is SESSION_CACHED_CURSORS = Value |
and cursor in Server Side ------------YES----V In these 3 cases we
Session Cursor cache? | know that the cursor has
| | already been parsed, so
NO | re-parsing is
| | unnecessary.
Is HOLD_CURSOR=Y |
and cursor in --------------YES----V
Held cursor cache? |
| |
NO |
| | ^
OPEN A CURSOR | CLIENT SIDE |
| | -------------|
Statement is Hashed and compared | SERVER SIDE |
with the Hashed value in the sql area | V
| V
Is it in sql area? --YES-(Soft Parse)--> ---------
| | |
NO | EXECUTE |
| | |
PARSE STATEMENT ('Hard' Parse)---------> ---------
SQL Parsing Flow Diagram
========================
Statement
Submitted
|
Is it in an open cursor?--------------YES----V
| |
NO |
| |
Is SESSION_CACHED_CURSORS = Value |
and cursor in Server Side ------------YES----V In these 3 cases we
Session Cursor cache? | know that the cursor has
| | already been parsed, so
NO | re-parsing is
| | unnecessary.
Is HOLD_CURSOR=Y |
and cursor in --------------YES----V
Held cursor cache? |
| |
NO |
| | ^
OPEN A CURSOR | CLIENT SIDE |
| | -------------|
Statement is Hashed and compared | SERVER SIDE |
with the Hashed value in the sql area | V
| V
Is it in sql area? --YES-(Soft Parse)--> ---------
| | |
NO | EXECUTE |
| | |
PARSE STATEMENT ('Hard' Parse)---------> ---------
来自 “ ITPUB博客 ” ，链接：https://blog.itpub.net/25845323/viewspace-1749715/ ，如需转载，请注明出处，否则将追究法律责任。
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