XML - Database

The variable values will be saved at a XML file. The structure of the database, tables and columns are defined at the XSD-file. With the function blocks FB_DBCreate and FB_DBTableCreate it is possible to create the XML file and the XSD file. Further information to work with XML files together with the TwinCAT3 Database Server, see XML information .

<?xml version="1.0" encoding="UTF-8"?>
<TestDB_XML xmlns:xs="http://www.w3.org/2001/XMLSchema-instance" xs:noNamespaceSchemaLocation="TestDB_XML.xsd">
  <myTable_Double>
    <row ID="1" Timestamp="2012-03-08T12:45:08" Name="TestValue1" Value="222.222" />
    <row ID="2" Timestamp="2012-03-08T12:45:14" Name="TestValue1" Value="222.222" />
    <row ID="3" Timestamp="2012-03-08T12:45:18" Name="TestValue1" Value="222.222" />
    <row ID="4" Timestamp="2012-03-08T12:45:22" Name="TestValue1" Value="222.222" />
    <row ID="5" Timestamp="2012-03-08T12:45:23" Name="TestValue1" Value="222.222" />
 </myTable_Double>
</TestDB_XML>

The variable values are saved in the following table structure.
Spaltenname	Datentyp	Null zulässig	Eigenschaft
ID	xsd:long	nein
Timestamp	xsd:dateTime	nein
Name	xsd:string	nein	80
ValueType="Double"
Value	xsd:double	nein
ValueType="Bytes"
Value	xsd:hexBinary	nein	längenwert

An AutoID is generated in the "ID" column. The value in this column is, in other words, always increased by 1.
The "Timestamp" column stores the time at which the data record was saved.
The name of the variable is stored in the "Name" column.
The "Value" column stores the value of the variable.

E_DBColumnTypes	XML	PLC Control
eDBColumn_BigInt	xsd:long	T_LARGE_INTEGER (TcUtilities.lib)
eDBColumn_Integer	xsd:int	DINT
eDBColumn_SmallInt	xsd:short	INT
eDBColumn_TinyInt	xsd:byte	BYTE
eDBColumn_Bit	xsd:boolean	BOOL
eDBColumn_Money	xsd:double	LREAL
eDBColumn_Float	xsd:double	LREAL
eDBColumn_Real	xsd:double	LREAL
eDBColumn_DateTime	xsd:dateTime	DT
eDBColumn_NText	xsd:string	STRING
eDBColumn_NChar	xsd:string	STRING
eDBColumn_Image	xsd:hexBinary	ARRAY OF BYTE
eDBColumn_NVarChar	xsd:string	STRING
eDBColumn_Binary	xsd:hexBinary	ARRAY OF BYTE
eDBColumn_VarBinary	xsd:hexBinary	ARRAY OF BYTE

Notice

Compact Flash Card Lifetime

Do not save the database on the Compact Flash Card in case of an embedded system.
Either use the database in RAM, i.e., do not save to the "Hard disk" folder, or save on a network folder. To many write cycles to the Compact Flash Card can shorten its service life.