Configuration

The SaF sub-system can be configured in four different modes, which can be grouped into volatile and persistent buffering modes:

Volatile buffer configurations
  • Main Memory

Persistent buffer configurations
  • Size Limited on Hard Disk (default)

  • Relative Size Limited on Hard Disk

  • Time Limited on Hard Disk

The persistent buffer configurations allow the specification of limits that control when data is being dropped. Here are two types of configurable limits:

Size limit

A soft limit on the maximum hard disk space to use.

Time limit

A hard limit on the age of stored data.

For size limits, the configurable retention mode determines if old or new data is dropped.

The limits are checked in 30 second intervals. If the SaF sub-system detects that a limit is reached, it starts deleting data from the persistent store and issues a warning message.

Configurations can be changed at runtime, see Configuration changes section for details. Individual configurations are described in the following sections.

Main Memory

Data is buffered in main memory. Different constraints apply, depending on the component in question:

Core
  • Real-time data which is to be archived is buffered until the configured maximum buffer size is reached. Old data is purged to make room for new data.

  • Log messages are buffered until the configured maximum buffer size is reached. Old messages are purged to make room for new ones.

  • Events are not processed at all.

Connector
  • Real-time data is not buffered at all.

  • Log messages are buffered until the configured maximum buffer size is reached. New messages are discarded if the buffer is full.

  • Events are not processed at all.

Size Limited on Hard Disk

Data is buffered on the hard disk persistently until the configured absolute size limit is reached. Note that the size limit may be lower than requested if the hard disk does not provide enough free space. If space is freed later, the limit will be recalculated.

If the size limit is reached, the configured retention mode determines if old or new items will be dropped to stay within the configured size limit.

Relative Size Limited on Hard Disk

Data is buffered on the hard disk persistently until the configured percentage of the hard disk’s capacity is reached. Note that the size limit may be lower than requested if the hard disk does not provide enough free space. If space is freed later or the disk capacity changes, the limit will be recalculated.

If the size limit is reached, the configured retention mode determines if old or new items will be dropped to stay within the configured size limit.

Time Limited on Hard Disk

Data is buffered on the hard disk persistently. If its source time-stamp is older then the current time minus the configured retention period, it will be dropped.

There is no overall size limit of the persistent buffer in this configuration.

Data Types

The following categories of data is buffered through the SaF system:

  • Real-time data (VQT)

  • Log messages

  • Alarms and events (A&E)

  • Audit Trail entries

  • Messages