Historian Tables (Reference)

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HistorianTable Configuration Properties

When configuring a HistorianTable, you need to specify some properties defining when and how data will be archived. The following table describes each of the properties available.

Save Quality

In certain instances, the graph may exhibit lines and values even in timestamps where there is no data present. For instance, when you access a graph that you know lacks data and you see a continuous line connecting the endpoints of existing data points, despite the absence of data in between, you can infer that you are leading with unreal information. If you click on such areas, the value shown can lead you to misleading cursor values, as no data exists for those specific moments.

To address this issue, you can remove the line connecting the points of the graph where there is no data. This can be achieved by enabling the SaveQuality property in your HistorianTable, as depicted in the image below. If the SaveQuality option is not available in any column, you can enable it by right-clicking on the top of any column name and select SaveQuality.

Creating Historian Tables

1. Navigate to Historian → HistorianTables
2. Click Plus icon
3. Configure properties:
   • Set TableName
   • Choose ArchiveLocation
   • Select trigger method
   • Configure deadbands
4. Click OK

<ac:structured-macro ac:name="info"> ac:rich-text-body Configuration Dependencies: Some options are mutually exclusive. For example, Normalized tables cannot use Triggers and must use SaveOnChange. </ac:rich-text-body> </ac:structured-macro>

Archiving Methods

SaveOnChange

Archives data when tag values change:

• Individual tag monitoring
• Respects deadband settings
• Efficient for sparse data
• Works with normalized schemas

Trigger-Based

Archives all table tags on trigger event:

• Synchronized timestamps
• Batch storage operations
• Supports time-based or event-based
• Standard schema only

Combined Approach

Using both SaveOnChange and Trigger:

• Primary: SaveOnChange for value changes
• Backup: Trigger ensures periodic storage
• Prevents data loss during steady-state

TimeDeadband Configuration

Prevents excessive database writes:

Format: HH:MM:SS:MS

Example Operation:

Interaction with Tag Settings:

• Tag Deviation can override deadband
• RateOfChange can force immediate storage
• DeadBand filters small changes

Schema Selection

Standard Schema

Best for:

• Synchronized data collection
• Trigger-based archiving
• Fixed tag groups
• Simple queries

Characteristics:

• One row per trigger/interval
• All tags share timestamp
• Fixed columns per tag
• Maximum ~200 tags per table

Normalized Schema

Best for:

• Asynchronous data
• SaveOnChange archiving
• Sparse data patterns
• Large tag counts

Characteristics:

• One row per tag change
• Individual timestamps
• Dynamic tag addition
• Unlimited tags per table
• No redundancy support

Data Retention

LifeTime Setting

Automatic data management:

• 0: No automatic deletion
• > 0: Delete data older than N days
• Runs daily maintenance job
• Frees storage space

Retention Strategies

SaveQuality Option

Stores OPC quality information:

Benefits

• Identifies bad/uncertain data
• Prevents interpolation over gaps
• Improves graph accuracy
• Supports data validation

Quality Values (OPC Standard)

• 192: Good quality
• 0: Bad quality
• 64: Uncertain quality

Visual Impact

• With SaveQuality: Gaps shown in trends
• Without SaveQuality: Lines connect all points

Trigger Configuration

Valid Triggers

• Tag values: Tag.ProcessValue
• Tag properties: Tag.ProcessValue.Quality
• Server objects: Server.Minute, Server.Second
• Expressions: Tag.Value > 100

Trigger Restrictions

• Server-side execution only
• No client tags allowed
• Single trigger per table
• Not available with Normalized

Common Triggers

Performance Optimization

Table Design Guidelines

1. Group by frequency - Similar update rates
2. Limit table size - 50-100 tags typical
3. Separate critical data - Priority tables
4. Match process dynamics - Related variables

Deadband Recommendations

Common Configurations

High-Speed Process Data

TableName: ProcessData
SaveOnChange: True
TimeDeadband: 00:00:01:000
Normalized: True
LifeTime: 30

Batch Records

TableName: BatchHistory
Trigger: Tag.BatchEnd
SaveQuality: True
LifeTime: 365

Regulatory Compliance

TableName: AuditData
SaveOnChange: True
SaveQuality: True
LifeTime: 2555
AutoCreate: True

Troubleshooting

Table not created:

• Check AutoCreate enabled
• Verify database permissions
• Review connection string
• Check table name validity

No data archived:

• Verify trigger configuration
• Check TimeDeadband setting
• Confirm tags assigned to table
• Review SaveOnChange setting

Excessive storage:

• Increase TimeDeadband
• Add tag deadbands
• Enable normalized schema
• Reduce retention period

Missing data points:

• Check SaveQuality setting
• Review trigger timing
• Verify tag quality
• Examine deadband values

Best Practices Checklist

• Plan table structure - Group logically related data
• Set appropriate deadbands - Balance detail vs storage
• Use SaveQuality - Track data reliability
• Configure retention - Manage storage growth
• Document tables - Use Description field
• Test before production - Verify archiving behavior
• Monitor performance - Track storage and query times
• Regular maintenance - Archive or purge old data

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