The user's responses are stored every time they click on Next. As responses are normally stored in a database, this can result in a bottleneck if a lot of questionnaires are running at the same time. Instead of writing questionnaires directly to the database, SoSci Survey offers the option of storing responses in a cache on the hard-disk.
Write caching reduces the burden on the database and the length of time taken between submitting a questionnaire page with “Next” and the information being stored. There is, however, no difference in the processing time taken to create the questionnaire (CPU time).
Generally speaking, your participants will not notice any difference. Server slots are freed up much more quickly which reduces the overall storage requirements (RAM) overall.
Note:: To ensure questionnaires are submitted regularly to the database, the script admin/crontask.php has to be run (Scheduled Tasks) at regular time intervals (min. every 60 minutes) when write cache is enabled. This script checks the current server workload and submits the questionnaires when the server is not so busy.