I'm using the Firebird 3.0 release version.  Delphi 10.1 Berlin with the firebird.pas release file and fbclient3.  I can connect to the database and can run queries, but I can't seem to get a custom transaction parameter block to work.   Here's my code:

    // Transaction := attachment.startTransaction(status, 0, nil);
    tpb := Util.getXpbBuilder(status, IXpbBuilder.TPB, nil, 0);
    tpb.insertTag(status, isc_tpb_write);
    tpb.insertTag(status, isc_tpb_read_committed);
    tpb.insertTag(status, isc_tpb_nowait);
    tpb.insertTag(status, isc_tpb_rec_version);
   
    // This always seems to error with "invalid format for transaction parameter block"
    Transaction := attachment.startTransaction(status, tpb.getBufferLength(status), tpb.getBuffer(status));

Has anyone gotten that to work?  Any suggestions are appreciated.  Also, does anyone know what the default transaction parameters are (e.g. if no custom tpb is used)?  Thanks for any help.

-Mark Ford