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Answered

Log size

Richard Staite 5 years ago in IQANdesign updated by Gustav Widén (System support) 7 months ago 4

Can anyone advise how big a log record is (analogue values) so that I can determinate the capacity of the logging memory in terms of number of records. Is all of the 64MB available for logging or is some reserved for system logs?


Hi Richard, The info I had from the IQAN team was MD4: 1 Mb = 40K 32 bit values stored. I think would be inclined to keep 1mb back for the system log.

Answered

Correct, each MB gives 40 000 events with timestamp and 32 bit value.


For the question about whether some is reserved for system log, there is a property on each log for log size, as percentage of maser module log memory, the default for the system log is 10%.

I know this is an old thread, but I am working on logging currently. For the 32 bit value, does that mean the channel name can not be greater than 32 bits? 

No, it is not the log record that is this size. The log record that is created is larger and contain more information such as time stamp and a reference to the channel. 

You can also have log records where the value takes up more space, when a log item is logging a channel of type text, each log record will be larger than when logging channels of other value types such as 32 bit Real.

So the estimate of 40 000 records per MB of log memory is only an estimate, the estimate is based on the assumption that most log records will be for values that with a value type that is 32 bit or less.