delphi oracle database connection

Use ADO socket connection:

conn:= '(DESCRIPTION = '+
       '(ADDRESS_LIST = '+
       '(ADDRESS = (PROTOCOL = TCP)(HOST = '+host+')(PORT = '+port+')) '+
       ' ) '+
       '(CONNECT_DATA =   '+
       ' (SERVICE_NAME = '+sid+')'+
       ' ) '+
       ' )';
  GDB:=TCPADOCONNECTION.Create(nil);
  GDB.ConnectionString:='Provider=OraOLEDB.Oracle.1;Password='''+psw+''';Persist Security Info=True;User ID='''+user+''';Data Source='+conn;
  GDB.Connected:=true; 

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please see this article.