Rockwell Automation 1756-HIST2G FactoryTalk Historian ME 2.2 - Manual (Page 291)

F • D ESIGN C ONSIDERATIONS AND L IMITATIONS
281
Trending is a higher priority task in the Logix controller than user application
programs. Trending too many tags at too low of a sample period can impact the
Logix controller’s ability to execute user application programs and cause task
overlaps.
When using FactoryTalk Historian ME, the user must ensure there is sufficient
Logix controller bandwidth to service trending without negatively impacting user
application programs.
CompactFlash Firmware
This section lists considerations related to the ControlFlash firmware.
A DDITIONAL M EMORY
Because the memory modules are special industrial grade modules, they are locked to
FactoryTalk Historian ME, and users can only purchase memory modules for the
FactoryTalk Historian ME module from Rockwell Automation.
FactoryTalk Historian ME firmware is stored in the CompactFlash along with the
customer’s data. The information cannot be read in other devices to protect the
intellectual property of Rockwell and its partners.
The CompactFlash meets higher thermal, shock and vibration specifications than
consumer grade flash memory.
P OWER L OSS
A minimal amount of data is lost if the module suddenly loses power and the file
system remains intact. Archived and snapshot data interruption occurs only during
the first minute of downtime.
In addition, power loss may prevent Data Collection from restarting, Data Transfer
from reconnecting if it was running, and other processes from restarting. If power
loss occurs, the module may need to be started using AOP in RSLogix 5000.
Performance
This section lists considerations related to performance.