problems with transactions in C++Builder

Greatings!

Help me please to resolve my problem.
As appeared, postgesql server doesn't rollback transaction
in C++ Builder environment. May be sombody have
an idea, how to make it work?
The test source in the bottom of the letter.

I will be very greatefull for any help.

Igor.

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CD->srvdb->StartTransaction();
CD->EQuery->Close();
CD->EQuery->SQL->Clear();
sprintf (str, "begin");
CD->EQuery->SQL->Add(str);
CD->EQuery->ExecSQL();

CD->EQuery->Close();
CD->EQuery->SQL->Clear();
sprintf (str, "lock mytable");
CD->EQuery->SQL->Add(str);
CD->EQuery->ExecSQL();

sprintf (str,"update mytable set \
active=1 where st = '2020201'" );

CD->EQuery->Close();
CD->EQuery->SQL->Clear();
CD->EQuery->SQL->Add(str);
CD->EQuery->ExecSQL();

CD->EQuery->SQL->Clear();
sprintf (str, "abort");
CD->EQuery->SQL->Add(str);
CD->EQuery->ExecSQL();
CD->srvdb->Rollback();

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the field "active" save new value = 1 after
'abort' command.