Location5

Location5 attribute is used for setting the write mode for sending archive data to the receiving Data Archive. Data can be written to Data Archive in three modes:

1. ARCAPPEND

2. ARCREPLACE

3. ARCNOREPLACE

   The following table lists and describes the supported write modes for PI3:

   Location5	Write Mode	Description
   0 (Default)	ARCAPPEND Archive and Snapshot Data	Add archive event regardless of existing events. Default snapshot behavior is to append data if event at timestamp exists.
   1 or 3	ARCNOREPLACE Archive Events Only	Add archive event unless event(s) exist at same time. Default snapshot behavior is to append data if event at timestamp exists.
   2	ARCREPLACE	Add archive event, replace if event at same time. Default snapshot behavior is to append data if event at timestamp exists.
   4	ARCREPLACE Archive and Snapshot Events	Add archive or snapshot event, replace if event at same time.
   5	ARCREPLACE Future Tags	Add archive event, replace if event at same time. Must be set for future tags.

   Caution: The PI Buffer Subsystem v3.4.375.38 only supports writing to the archive in ARCNOREPLACE mode. ARCNOREPLACE mode prevents the PI to PI interface from honoring Location5 archive write options and can lead to data loss. AVEVA recommends using a newer version of PI Buffer Subsystem to avoid this issue.

   Caution: By default (Location5 = 0) in-order data sent to the target server's snapshot will flow into the archive in ARCAPPEND mode; however, Location5 can be set to override the default behavior (Location5 = 2 or Location5 = 4) and replace data in the target Data Archive. Using the override behavior can lead to mismatches between data in the source and target Data Archives, since the default behavior on the source server is to append duplicate events.

The write order established by Location5 applies to both in-order and out-of-order data received from the source Data Archive. The write order established by Location5 also applies to all three modes of source Data Archive data retrieval modes:

• Exception based source data retrieval for PI points configured to scan class 1 (Location4 = 1).

• Archive based source data retrieval for PI points configured to scan classes other than 1 (Location4 > 1).

• History recovery mode, specified using either the command line parameter /HRONLY or by using the HISTONLY INI file setting.

Caution: In PItoPI, scan classes can be exception based or archive based. If an interface point is configured with a source PI point that has the potential to receive an out of order event for edit/replace/add, then the interface point must be assigned to the exception scan class: scan class 1 for the PI to PI interface. The interface point must not be assigned to an archive based scan class. A typical example is a PI to PI interface point whose source point receives laboratory data.

Note: Only one scan class in any interface copy can sign up for exceptions, the other scan classes can obtain only archived data. By default, the scan class that signs up for exceptions is the first scan class listed on the command line.

Exception based data retrieval mode

The exception scan class (scan class 1 for the PI to PI interface) writes all source out-of-order data to the destination Data Archive using the write mode specified in Location5.

Archive based data retrieval mode

An archive based scan class (any scan class other than 1 for the PI to PI interface) is not aware that source data may be out-of-order. It simply reads data from the source archive after the data is archived. The order in which that data arrived on the source server is irrelevant.

The PI to PI interface will honor Location5's ARCAPPEND and ARCREPLACE modes on a PI3 server for duplicate events when interface points are configured to use an archive based scan class. The PI to PI interface will not honor the ARCNOREPLACE mode on a PI3 server for interface points configured to use an archive based scan class.

History recovery mode

History recovery mode is specified using the /HRONLY command line parameter or the Histonly INI file setting. In the history recovery mode of operation, the interface performs PI Data Archive reads on the source server, typically for backfilling purposes on the target Data Archive. Scan classes are irrelevant when operating in this mode. History recovery mode will honor all write modes (ARCAPPEND, ARCREPLACE, and ARCNOREPLACE) for out-of-order data (relative to the target Data Archive Snapshot value) on a PI3 server.