The information available in ClearSCADA is stored in different places called streams. This allows separation of data on disk, the main benefit is for performance reasons, however different streams are structurally different for the specific information they store. The different streams are listed below:
Name
Number of Streams per Server Instance
Examples
Notes
Config
1 for ClearSCADA 2009 R1 and earlier.
Multiple for ClearSCADA 2009 R2 and later, 1 per 16384 object Ids.
Information that doesn't change often:
Point limits and anything shown when you click Properties.
Logic programs code
Mimic content
Data grid structure and content
Data table structure (not content)
Stored in ClearSCADA.Dat, ClearSCADAConfig.Dat or ClearSCADAConfig0000.dat (and ClearSCADAConfigStr.dat) depending on the version
Synchronised between servers
Flushed to disk only when config has changed (every minute)
Saving can have a noticeable performance hit on large databases
Is required to run the database
Memory resident
Data
1 for ClearSCADA 2009 R1 and earlier.
Multiple for ClearSCADA 2009 R2 and later, 1 per 16384 object Ids.
Information that changes frequently:
A point's CurrentValue and CurrentTime
A variable's value
Stored in ClearSCADAData.Dat or ClearSCADAData0000.Dat depending on the version
Synchronised between servers
Flushed to disk only when data has changed (every minute)
Usually partnered with the config stream, however this stream is not strictly necessary to successfully start a database
Memory resident
Dynamic
1
Runtime information that doesn't need to be retained on startup:
Outstation's current request
Channel's current state
Synchronised between servers
Not stored on disk, this means on a cold restart all information is discarded
Metadata
1
Extra properties added to objects
ClearSCADAMetadata.dat
XML file, edited via ViewX (Edit Metadata off root group)
Flushed to disk on change
Synchronised between servers
New in ClearSCADA 2009 R1
Lack of file on database start may cause some configuration to be lost
Memory resident
Archive
1
Archive volume index.
Stored in ClearSCADAArchive.dat
Not synchronised between servers (each server has its own local index)
Saved following each archive operation
Single-purpose stream
Files
Multiple, 1 per 'CHisFiles' aggregate
Historical Crystal Reports
Archived configuration permits
EMS safety reports and switching plans
MGX configuration upload reports
TMX configuration mismatch reports
Synchronised between servers
Stored in Files directory
Disk resident
Historic
Multiple, 1 per 'CHistory' aggregate
Point historic data
Synchronised between servers
New records saved to disk every minute
Stored in History directory
Single-purpose stream
32 bytes per record
Disk resident, with a small memory cache
Journal
Multiple, many objects to one stream.
Object event data and messages
Synchronised between servers
New records saved to disk every minute
Number of streams = (current maximum object id in database/stream size)
Stream size can be tweaked for bigger systems.
Stored in Journal directory
Single-purpose stream
768 bytes per record
Disk resident, with a small memory cache
DataFiles
Multiple, 1 per type of file for each relevant object
Contents of data tables
Crystal Report definition (new in ClearSCADA 2009 R1)
Latest Crystal Report (new in ClearSCADA 2009 R1)
Synchronised between servers
Stored in DataFiles directory
New in ClearSCADA 2007 R1
Disk resident, some objects provide option to cache in memory
ConfigChanges
Multiple, many objects to one stream
Changes to configuration properties stored historically
Disabled by default
Synchronised between servers
New in ClearSCADA 2010 R1
New records saved to disk every minute
Number of streams = (current maximum object id in database/stream size)
Stream size can be tweaked for bigger systems.
Single-purpose stream
1280 bytes per record
Disk resident, with a small memory cache
AlarmSummary
Multiple, many objects to one stream.
Summarized alarm state changes
Disabled by default
Synchronised between servers
New in ClearSCADA 2015 R1
Old records saved to disk every minute (saved after full transition ON-OFF and new ON)
Number of streams = (current maximum object id in database/stream size)
Stream size can be tweaked for bigger systems.
Stored in AlarmSummary directory
Single-purpose stream
3304 bytes per record
Disk resident, with a small memory cache
The database schema can be used to determine if a property is either a Data or Config stream property, however as a rule of thumb if the property is configurable in the Properties dialogue of an object that property is stored in the Config stream.
The performance impact of the Config stream is that the Config stream is bigger than the Data stream, as such it takes longer to save and requires a longer duration of a lock on the ClearSCADA database. The Data stream is kept small to allow quicker saving, whereas the Config stream has "the rest of the information", usually resulting in the Config stream being approximately five times the size of the Data stream. Because of this impact, configuration changes should be kept to a minimum when using automated tools to change them (i.e. logic and external programs), these programs can change the config often rendering the performance improvement usually seen as minimal. Rapidly changing data should be stored in data properties instead of config properties.
Data grids are also stored in the Config stream and so they are not good as a store for constantly changing data as a change requires a save of the entire config stream for that object, whereas data tables are stored in the DataFiles stream and are more efficient in their storage and transfer.
