About block gaps

AVEVA Historian is designed to store data in a contiguous series of history blocks. But there are two cases that may result in block gaps -- that is, gaps between the history blocks:

• If no data was acquired for the timeframe corresponding to a particular history block, that block will not be created.

• If a history block is deleted for whatever reason, a block gap will result.

By default, gaps in data are charted (for example, by Trend and Insight) as straight lines. If you want data gaps to display as empty, you can change the Windows Registry settings.

To change Windows Registry settings to show block gaps

1. From the Start menu, run RegEdit.

2. Navigate to:

   HKEY_LOCAL_MACHINE -> SOFTWARE -> ArchestrA -> Historian -> Programs -> aahRetrieval

3. Create a DWORD Value called UseBlockGaps and set it to "1".

   1. Right-click aahRetrieval, select New, and then select DWORD.

      

   2. Type "UseBlockGaps" as the name of the new item.

   3. Right-click UseBlockGaps and select Modify.

   4. In Value data, type "1".

      

4. Exit RegEdit.

   Note: If data is later inserted (for example, using a data update process) in a gap, the history block(s) will be created or recreated. In that case, the Block Gap option is set to OFF, and any tags that were not updated will show as flatlined data.