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dbms_alert on RAC

Not long time ago, I came across a usage of dbms_alert to manage running jobs. As the solution implemented must work also for RAC, I wanted to know whether dbms_alert works on RAC across instances.

The documentation nor Metalink does not say anything (contrary to dbms_pipe, which does NOT work on RAC). So, if they don't warn, it should work... However, Julian Dyke says, that dbms_alert does not work and is the same as dbms_pipe (sources: http://juliandyke.com/Presentations/Presentations.html#ARoughGuideToRAC, page 17, or Pro Oracle Database 10g RAC on Linux, page 426).

You know, never trust anybody, so I conducted a test case (10.2.0.3 on Linux x86_64, VMware ESX server, 2-node RAC):

You will need two simultaneous sessions, I mark them with DWH1> and DWH2> here.
DWH1> select instance_name from v$instance;

INSTANCE_NAME
----------------
DWH1

DWH2> select instance_name from v$instance;

INSTANCE_NAME
----------------
DWH2

DWH2> exec dbms_alert.register('TST');

DWH2> set serveroutput on


DWH2> declare
message varchar2(2000);
status integer;
name varchar2(2000);
begin
DBMS_ALERT.WAITANY (
name ,
message,
status);
dbms_output.put_line(name);
dbms_output.put_line(message);
end;
/

DWH1> exec dbms_alert.signal('TST','msg1');

DWH2> TST
msg1

PL/SQL procedure successfully completed.

DWH2> declare
message varchar2(2000);
status integer;
begin
DBMS_ALERT.WAITONE (
'TST',
message,
status );
dbms_output.put_line(message);
end;
/

DWH1> exec dbms_alert.signal('TST','msg1');

msg1

PL/SQL procedure successfully completed.

So, as you see, it works even on RAC. Just test it yourself, and never trust anybody anything without proper testing. Everyone does mistakes.

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