Oracle Database Discussions

hi,

my database is 10.2.0.1...by default optimizer_mode=ALL_ROWS..

for some sessions..i need rule based optimizer...

so can i use

alter session set optimizer_mode=rule;

will it effect that session only or entire database....
and following also.i want to make them at session level...

ALTER SESSION SET "_HASH_JOIN_ENABLED" = FALSE;



ALTER SESSION SET "_OPTIMIZER_SORTMERGE_JOIN_ENABLED" = FALSE ;



ALTER SESSION SET "_OPTIMIZER_JOIN_SEL_SANITY_CHECK" = TRUE;



will those effect only session or entire database...please suggest