| CitectSCADA 7.0, by default, will
limit the number of bytes written per write request to 16,384 bytes
before sleeping. This is controlled by the [Trend]
BytesWrittenBeforeSleep citect.ini parameter. The help file
suggests that this parameter can be set to a maximum of 1,000,000
bytes, which is true but only for writing to the trend files at
runtime . On start-up this parameter will only
make a difference up to 32,768 bytes. Any value above that, will be
capped to 32,768 bytes by CitectSCADA.
This is however only one of a number of factors that may
affect the performance of Trend History File creation at start-up.
Keep in mind that having a trend system which has a large number of
history files with small file sizes may experience lower write
speeds as there is added overhead for the creation of each
file.
It is good practice to minimise the amount of trend data that
you're storing with CitectSCADA. You should focus on trending
values that are important to end users rather than trying to trend
each variable tag in your project. Also, you should avoid trying to
store multiple years worth of trend data, especially if you have a
large number of trends. If you require such functionality then we
recommend that look at using the Historian component of CitectSCADA
Reports.
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