Connect to Oracle when service is starting...

[rdeutsch]

I am writing a serviceapplication with doa. When the service is starting after a reboot of the server - how can the service detect that oracle is running.

 

[KaeOl]

You can check the availability of Oracle by using TOracleSession.CheckConnection. If connection has lost, you can use the method TOracleSession.Reconnect to reinstall the connection.

------------------
Oliver Kaesmann

 

[Marco Kalter]

If you attempt to make a connection with a database instance that is not started you should get an ORA-01034 error (ORACLE not available). You can test for this in your service:

try
  MySession.Connected := True;
except
  on E: EOracleError do
  begin
    if E.ErrorCode = 01034 then
      ShowMessage('Instance not started')
    else
      ShowMessage(E.Message);
  end;
end;

------------------
Marco Kalter
Allround Automations

 

[phocai]

Is TOracleSession.Reconnect still a valid method? It's not in the documentation. It worked with v3.4.6.4 but when I tried to recompile with v4.0.7 I received an error: "Undeclared Identifier: 'Reconnect'".

Should TOracleSession.CheckConnection(Reconnect: Boolean) be used instead?

Thanks.

 

[Marco Kalter]

Yes, you should use CheckConnection.

 

[phocai]

Thanks.

 

[Roeland]

How should we react when the connection with Oracle is lost?

Is a Reconnect property (boolean default True) not a valid option? Should the OracleSession not check the connection before each transaction?

Or, if this is too much overhead, an OnConnectionLost event where we can try to reconnect.

 

[Marco Kalter]

This would indeed cause some overhead. It may also require additional application logic to recover from a lost connection, depending on where, when and how the connection was lost. It's not so easy to handle this completely transparent in the background.

 

[Roeland]

What about the OnConnectionLost event? Could this be added?

 

[Marco Kalter]

Technically this is possible. I have added it to the list of enhancement requests.