Re: Direct SGA access problem because of structs' changing start addre

>... how to find a starting address without query a instance

You can obtain the address of fixed SGA variable "ksusga" directly from Oracle binary:

$ nm $ORACLE_HOME/bin/oracle | grep ksusga_

Inside this "ksusga" structure in SGA you can find the pointer to the array,  which holds pointers to each session slot of x$ksuse. Its offset depends on Oracle version and port, but is independent of current instance parameters.

"ksusga" also contains pointer to pointers to x$ksupr slots and the values of "sessions" and "processes" parameters as well.

See Tanel Põder post
http://www.freelists.org/post/oracle-l/Using-Unix-debuggers-to-attach-to-Oracle-processes,10 and Julian Dyke presentation
http://www.juliandyke.com/Presentations/SGAInternals.ppt

Best Regars
Andrey Nikolaev
http://andreynikolaev.wordpress.com/

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