来自AskTom的关于SoftParse的解释

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Therearetwotypesofparses(well,actually"three"thesedays).

Theyare

oHARDparse--thequeryhasneverbeenseenbefore,isn'tinthesharedpool. 
Wemustparseit,hashit,lookinthesharedpoolforit,don'tfindit,
securitycheckit,optimizeit,etc(lotsofwork).

oSoftParse--thequeryhasbeenseenbefore,isinthesharedpoo. Wehave
toparseit,hashit,lookinthesharedpoolforitandfindit(lessworkthen
ahardparsebutworknonetheless)

oakinder,softerSoftParse--youareusingsession_cached_cursors(search
thissiteforthatwordforinfo). Wetakeyourquery,lookinthesessions
cursorcache--findthecursorandreuseit. Veryverylittlework.

So,after"startup",yougointosqlplusanddothis:

SQL>altersessionsetsession_cached_cursors=0;--justmakingsurethisisoff
SQL>select*fromemp; --hardparse
SQL>select*fromemp;--SoftParse
SQL>select*fromemp;--SoftParse
SQL>altersessionsetsession_cached_cursors=100;--enablethisfeature
SQL>select*fromemp; --SoftParse
SQL>select*fromemp;--kinder,gentler,SoftParse

link：

http://AskTom.oracle.com/pls/ask/f?p=4950:8:::::F4950_P8_DISPLAYID:801662252143



 
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