This is a subtype of the Byte DataTypewith the OptionSetValues Propertydefined. It is used to indicate how the Valueof a Variablecan be accessed (read/write) and if it contains current and/or historic data. The AccessLevelTypeis formally defined in Table 40.

Table 40– AccessLevelType Definition

Name

Bit

Description

CurrentRead

0

Indicates if the current value is readable. It also indicates if the current value of the Variableis available.(0 means not readable, 1 means readable).

CurrentWrite

1

Indicates if the current value is writable. It also indicates if the current value of the Variableis available (0 means not writable, 1 means writable).

HistoryRead

2

Indicates if the history of the value is readable. It also indicates if the history of the Variableis available via the OPC UA Server.(0 means not readable, 1 means readable).

HistoryWrite

3

Indicates if the history of the value is writable It also indicates if the history of the Variableis available via the OPC UA Server.

(0 means not writable, 1 means writable).

SemanticChange

4

This flag is set for Propertiesthat define semantic aspects of the parent Nodeof the Propertyand where the Property Value, and thus the semantic, may change during operation.

(0 means is not a semantic, 1 means is a semantic).

StatusWrite

5

Indicates if the current StatusCodeof the value is writable

(0 means only StatusCodeGood is writable, 1 means any StatusCodeis writable).

TimestampWrite

6

Indicates if the current SourceTimestampis writable

(0 means only null timestamps are writable, 1 means any timestamp value is writeable).

Reserved

7

Reserved for future use. Shall always be zero.