Migration considerations

PI Web API 2019 SP1 adds support for OMF simple type messages and limited OMF migration support. If you are migrating from a previous version of OMF to PI Web API 2019 SP1, you should be aware of the following:

• OMF resources may have their PI AF or Data Archive representation changed.

• Existing PI AF or Data Archive resources that were not created using OMF may be migrated.

• When a CREATE CONTAINER message is received, if the container already exists, it will be migrated.

  Simple versus Complex Dynamic Type Messages

  The following table shows a result comparison between simple and complex type messages:

  Comparison Detail	Simple dynamic type	Complex dynamic type
  Type message	[ { "id": " simple-dynamic-type1", "version": "1.0.0.0", "type": "object", "classification": "dynamic", "properties": { "time": { "type": "string", "format": "date-time", "isindex": true }, "attribute1": { "type": "string" } } } ]	[ { "id": " complex-dynamic-type1", "version": "1.0.0.0", "type": "object", "classification": "dynamic", "properties": { "time": { "type": "string", "format": "date-time", "isindex": true }, "attribute1": { "type": "string" }, "attribute2": { "type": "string" } } } ]
  Container created	[{ "id": " simple-container1", "typeid": " simple-dynamic-type1" }]	[{ "id": " complex-container1", "typeid": " complex-dynamic-type1" }]
  PI Points created in version 2019	simple-container1.attribute1	complex-container1.attribute1 complex-container1.attribute2
  PI Points created in version 2019 SP1	simple-container1	complex-container1.attribute1 complex-container1.attribute2

The difference between how PI points were created affects how they will be migrated to PI Web API 2019 SP1. PI points are grouped in the following categories for migration:

• PI points created by OMF (PI Web API 2019 and 2019 SP1) contain valid Point Source and Extended Descriptor attributes.

• PI points that were not created by OMF have an Extended Descriptor attribute that PI Web API cannot parse.

For PI points created using OMF (PI Web API 2019) from containers created by simple dynamic type messages, the PI points are renamed from simple-container1.attribute1 to simple-container1.

For PI points created using OMF (PI Web API 2019), but not from containers created by simple dynamic type messages, and for PI points not created using OMF, the PI point attributes are overwritten.

PI Web API 2019 SP1 adds the following key/value pair to the PI point Extended Descriptor attribute: OmfSchemaVersion=1 to identify the schema version of OMF used to create the PI point. If you send a container message for PI points created by PI Web API 2019 after migrating to PI Web API 2019 SP1, the Extended Descriptor attribute is updated to include OmfSchemaVersion=1.

PI Asset Framework determines whether existing point type conversion is possible. PI Web API does not check for any potential issues.

PI Web API 2019 did not store the container description. PI Web API 2019 SP1 stores the container description in the Descriptor attribute for all PI points that are created by container. This change affects migration by overwriting any existing point descriptor with the container description field, or by removing current point descriptor if the container description is omitted.

For all PI points migrated to or created by PI Web API 2019 SP1, the Descriptor attribute is validated as a part of the Create Container messages, checking for point equivalence. If a container does not have a description field, PI points overwritten by this container will have an empty Descriptor attribute.