OCIErrorGet raise Access violation when Error = 12543

[Devil]

In my appliction when database alias is wrong i need catch this error
(for example in tnsnames.ora I create some alias testdb of database for
tnsping testdb return TNS-12543 TNS:destination host unreachable)

I do this code in my program:
try
//ReturnCode := FSourceOracleQuery.Session.ReturnCode; //It's OK!!!
if not FSourceOracleQuery.Session.Connected
and
(FSourceOracleQuery.Session.CheckConnection(True) = ccError)
then raise EOracleError.Create(FSourceOracleQuery.Session,
FSourceOracleQuery.Session.ReturnCode,
FSourceOracleQuery);

except
on E: EOracleError do
begin
if E.ErrorCode = 12543
then begin
WriteToLog(E.Message, mtError);
raise;
end;
end;
end;

But, in EOracleError.Create constructor on line:
{Error = 12543}
OCIErrorGet(OCIError(Error), 1, nil, ub4(Error), Msg, SizeOf(Msg), OCI_HTYPE_ERROR);
raised Access violation at address 60601FC5 in module 'OraClient9.Dll'. Read of address 000030FF

and except ... end block not executed.

Why raise Access Violation?
Perhaps TNS-12543 is TNS error and not OCI and in OraClient9.Dll not entry for error OCIError(Error), where Error = 12543.

Who help me please?

Or who tell me another way for raise EOracleError.Create?

 

[Devil]

I partially solve this problem, but actually i think that is not perfect solution
and the best there is raise EOracleError.

My solve this problem:
if not FSourceOracleQuery.Session.Connected
and
(FSourceOracleQuery.Session.CheckConnection(True) = ccError)
then begin
ReturnCode := FSourceOracleQuery.Session.ReturnCode;
if ReturnCode = 12543
then begin
raise Exception.CreateFmt('TNS:destination host unreachable for database alias: %s', [FSourceOracleQuery.Session.LogonDatabase]);
end
else begin
raise EOracleError.Create(FSourceOracleQuery.Session,
FSourceOracleQuery.Session.ReturnCode,
FSourceOracleQuery);
end;
end;

Please write your solve for this problem or what your think?

 

[Devil]

Or how get ErrorMessage for my nlslanguage from Oracle Error Server Messages for Error code 12543 not using function: OCIErrorGet(OCIError(Error), 1, nil, ub4(Error), Msg, SizeOf(Msg), OCI_HTYPE_ERROR);

 

[Devil]

For ErrorMessage by ErrorCode I find solve:
raise Exception.Create(FSourceOracleQuery.Session.ErrorMessage(ReturnCode));

Another question is relevant(important)

 

[Marco Kalter]

This error:

raised Access violation at address 60601FC5 in module 'OraClient9.Dll'. Read of address 000030FF

indicates an Oracle Client bug. There is not much one can do with such an Access Violation.

 

[Devil]

And what i do?
I was use:
raise Exception.Create(FSourceOracleQuery.Session.ErrorMessage(ReturnCode));

instead of:
raise EOracleError.Create(FSourceOracleQuery.Session, FSourceOracleQuery.Session.ReturnCode, FSourceOracleQuery);
???

For example in pl/sql developer on Oracle logon database form for TNS-12543 TNS:destination host unreachable not generated Access Violation and shown message with text of error.
How we do this or processed it?