QlikView and Qlik Sense files are like ZIP file, as in they are highly compressed. So obtaining an estimate of how much RAM is needed for loading Apps into memory (footprint) is difficult to provide across the board. The expected memory usage associated with the app can also depend on how many users access the app and how much they are used.
Environment :
- QlikView, all versions
- Qlik Sense Enterprise on Windows, all versions
Resolution:
An estimate of the RAM needed per app can be built on the below, but for accuracy always test by loading the app into memory and using the Qlik Scalability Tools to obtain a baseline of memory usage for each app as it is accessed by the foreseeable number of users.
Telemetry logging which allows for using the Telemetry Dashboard, is also an available suitable tool.
Since the release of the February 2019 version, Sense System Performance Analyzer monitoring App can be used to determine app footprint as well. Since the release of the June 2018 version, App Metadata Analyzer monitoring App can also be used. However, these last three may not provide the same data as the Scalability Tools.
An alternative is to use a test environment and simply observe RAM usage increases as apps are first opened (footprint), and as number of users accessing the app increase, then as number of operations are performed within the app. The test environment results for observed memory and CPU usage can be recorded as a baseline for the particular app in production, which assists in determining future sizing/scaling needs.
RAMInitial = SizeOnDisk × FileSizeMultiplier ; this is the initial RAM footprint for any application
FileSizeMultiplier: range between 2-10 (this is a compression* ratio depending on the data contained in the app)
*Compression is based upon the data, and how much we can compress depends upon the homogeneity of the data. The more homogeneous, the more compression Qlik can achieve.
More information on one way of optimizing a document can be found on the Qlik Design Blog: Symbol Tables and Bit-Stuffed Pointers
RAMperUser = RAMinitial × userRAMratio ; this is the RAM per each incremental user
userRAMratio: range between 1% -10%
Total RAM used per app :
TotalRAM = (RAMperUser × Number of users) + RAMinitial
Example:
SizeOnDisk = 1 GB
File Size Multiplier 6 (range is from 2 to 10)
RAMinitial = 1 * 6 = 6 GB
If we take a RAM Ratio per User of 6% then it is 0.06 (range is from 1 to 10)
RAMperUser = 6 x 0.06 = 0.36GB
Then RAM Required for 30 Users
TotalRAM = (RAMperUser × No. users) + RAMinitial
TotalRAM = (0.36 * 30) + 6
TotalRAM = 16.8 GB
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