Application contexts in multi-user environments

Question

[Oracle9i Enterprise Edition Release 9.2.0.3.0]
Hi,
I'm experimenting with application contexts as a means of utilizing bind variables in variable WHERE clauses.
In a multi-user environment where the database is accessed from an application using a single user id, are there any conflicts involved when the same procedure is accessed multiple times and the same context variable is set to different values by each call? In other words, can I assume that between the time the user_id of my_context is set and the query is executed in procedure call 1 that those values will be used and not be affected by other procedure calls also setting the user_id of my_context?
Thanks,
Ed Holloman
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create or replace context my_context using my_proc;
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In procedure call 1 to my_proc:
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my_query := 'SELECT * FROM my_table ' ||
'WHERE user_id = sys_context(''my_context'',''user_id'')';
dbms_session.set_context('my_context', 'user_id', '12345');
OPEN my_refcursor FOR
my_query;
================================================
In procedure call 2 to my_proc:
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my_query := 'SELECT * FROM my_table ' ||
'WHERE buyer_id = sys_context(''my_context'',''user_id'')';
dbms_session.set_context('my_context', 'user_id', '45678');
OPEN my_refcursor FOR
my_query;
================================================
etc.

Answer 1

A quick little test shows John's statement in action:
sql>create or replace procedure test_procedure
  2    (p_value in  pls_integer,
  3     p_rc    out sys_refcursor)
  4  is
  5  begin
  6    dbms_session.set_context('TEST_CONTEXT', 'VALUE', to_char(p_value));
  7    open p_rc for select sys_context('TEST_CONTEXT', 'VALUE') from dual;
  8  end;
  9  /
Procedure created.
sql>var rc1 refcursor
sql>var rc2 refcursor
sql>exec test_procedure(1, :rc1)
PL/SQL procedure successfully completed.
sql>exec test_procedure(2, :rc2)
PL/SQL procedure successfully completed.
sql>print rc2
SYS_CONTEXT('TEST_CONTEXT','VALUE')
2
1 row selected.
sql>print rc1
SYS_CONTEXT('TEST_CONTEXT','VALUE')
1
1 row selected.Note the original value (1) has not been stomped on by the second execution even though we fetched this after that second execution and fetch sequence.