Rockwell Automation FactoryTalk Historian SE 4.0 Live Data Interface User Guide - Manual (Page 22)

Chapter 4 Point Source
22 Rockwell Automation Publication HSELD-UM024A-EN-E–September 2013
If a Point Source character is not explicitly defined when creating a
PI point, the point is assigned a default Point Source character of
Lab (PI 3). Therefore, do not use Lab as a Point Source character for
an interface to avoid confusion.
IMPORTANT
Do not use a Point Source character that is already associated with
another interface program. However, it is acceptable to use the same
Point Source for multiple instances of an interface.