set_session_spec

set_session_spec 
      ::= 
      ( ( ( "sql_trace" | "global_names" ) "=" ( "true" | "false" ) ) 
      | ( "nls_language" "=" language_name ) 
      | ( "nls_territory" "=" territory_name ) 
      | ( "nls_date_format" "=" date_format ) 
      | ( "nls_date_language" "=" language_name ) 
      | ( "nls_numeric_character" "=" quoted_string ) 
      | ( "nls_iso_currency" "=" territory_name ) 
      | ( "nls_currency" "=" quoted_string ) 
      | ( "nls_sort" "=" ( sort_name | "binary" ) ) 
      | ( "optimizer" "goal" "=" ( "all_rows" | "first_rows" 
      | "choose" | "rule" ) ) ) 

This rule is called by

alter_session