BDE Performance

The BDE (Borland Database Engine) stands as an intermediate layer between your C++ Builder program's data components and the actual DBMS (DataBase Management System - for instance Access or dBase). It offers special services, in some cases providing services not normally provided by the underlying DBMS (such as transactions), and in other cases providing services which cross DBMS boundaries, such as heterogenous joins (SELECTs which join two or more tables, each from a different database or even a different DBMS).

For, small tables, BDE performance is generally good. However, when your database tables become larger, you may need to change certain BDE parameters, especially when you are iterating through all of the rows in a table.

On my system, a Pentium 120 with 32 Mb RAM, the following settings worked well for a 8,000 row local dBase table, with performance results discussed below. The default settings worked fine for tables of 500 rows.

BDE parameters are set in BDECFG32.EXE. In BDE 3, go to the System page. Change the following:

MINBUFSIZE	to 2048
MAXBUFSIZE	to 8152
MAXFILEHANDLES	96
LOWMEMORYUSAGELIMIT	64
SHAREDMEMSIZE	2048

With these settings, my test program scanned 8,000 rows (performing a field access on each row and updating a screen row count in a TLabel) in about 25 seconds, a performance of 19,440 rows per minute.

The following is the test program:

void __fastcall TBDETestForm::LoopButtonClick(TObject *Sender)
{
   if (TestDatabase->LargeTable->FindFirst())
   {
      int Index = 1;

      do
      {

         AnsiString ID 
      = TestDatabase->LargeTable->FieldByName("ID")->AsString;

         RowDisplay->Caption 
      = Index++;

         ColumnDisplay->Caption 
      = ID;

         Application->ProcessMessages();
      }
      while (TestDatabase->LargeTable->FindNext());
   };
}