Santhosh Kumar

• Sep 4th, 2006

 

Processing Of Sql select statement: When any user executes any sql statement a user process generated and it the request sents to server process. First Server process checks for any privious execution of statement(execution plan) is available inLibrary cache if the execution plan is availble it uses tht path and it fetches the required data from the datafiles and put into database buffer cache and then sends to userprocess. If execution plan is not there in the library cache then the statement enters into parsing state in which validations are performed like object is existing or not. after parsing it goes to datadictionary cache to find the definations of the object and takes the data from the datafiles and fetches the required data from datafiles to database buffer cache and sends to user process. Its a question should hav to explaing with a memory diagram through tht every one can easily understood .

rajendra singh chauhan

• Mar 20th, 2007

 

When a select statement is executed first of all the statements hash code is genrated then that hash code is matched in library cache if the hash code matched then statement is directly executed and if the hash code is not present then hard parsing is done and statement is executed