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Warning - Platform running low on RAM disk space (Niagara G3 Release 3.2.5 and higher)

Issue

Warning - Platform running low on RAM disk space (Niagara G3 Release 3.2.5 and higher)

Environment

I/A Series G3 (typically embedded ENC/JACE platforms)

Cause

Low disk warning for history RAM disk A station fault will be generated if the free disk space on the history / alarm RAM disk falls below the minimum percentage specified on the PlatformServices property sheet.

Resolution

During station startup,  /niagara/bin/ramdisk.sh is invoked to create the RAM disk partition.   The RAM disk is named /aram0 and symbolic links are created from /alarm -> /aram0/alarm /history -> /aram0/history.  After the RAM disk is created it is populated with the contents of the alarm.zip and history.zip files.  During a station save or shutdown, the alarm and history files on the RAM disk are zipped and stored under the station directory in alarm/alarm.zip and history/history.zip. 

If this fault occurs, users should take one or more of the following actions to prevent history/alarm data from being lost:

  1. Reduce number of histories that you are collecting
  2. Reduce number of records in each history
  3. Increase history RAM disk system (requires reboot).

Action 3, above, will reduce the available system memory and should only be taken if there is sufficient free system memory.  Rather than writing history and alarm records directly to persistent storage, a Niagara G3 station stores history and alarm records in a RAM disk. This approach reduces the number and frequency of writes to flash.  Be careful not to increase too much otherwise you risk consuming all the available JACE free RAM causing the niagarad to crash.  Review the free system memory and make sure to leave a buffer of at least 1 MB of free RAM.  The RAM disk size is stored in /niagara/lib/platform.bog and can be adjusted using Services -> Platform Services.

After reducing the number of histories, etc. the RAM disk will still indicate a low warning message until the unused histories are removed from the history storage.  Delete the unused histories using the Database Maintenance view on the history component view within the station.

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