For reference:

UBBdev uses MyISAM disk based for ONLINE and TOPIC_VIEWS temporary tables, because there are very few members logging in (all public discussions are free to view and download on UBBDEV). The topic views are rarely updated until a new post is created, or someone logs in to trigger their updates. It also gets a ton of traffic and spiders, which sometimes makes the ONLINE list very large.

My larger UBB.threads forums, are all stock database settings of MEMORY for ONLINE and TOPIC_VIEWS temporary tables. I have had zero issues with their stock settings. But I also keep their ONLINE time frame to a reasonable 10 minutes to 60 minutes. Never had an issue.

Its rare that you would want to make this setting change. But now it is documented here on UBBCentral.com for others to review and adjust as they feel are needed.


EDIT:
Further research takes me to a discussion over here:
https://dba.stackexchange.com/quest...o-use-the-memory-storage-engine-in-mysql

Since I only came in to working as an official developer of UBB.threads in 2015 (beginning with version 7.5.9), I believe we may need to revisit the need for having these two tables in memory storage, as was decided in 2007 for UBB.threads 7.1.0... from the days of MySQL 4.x/5.1, PHP 4.x, and 5400 RPM HDDs being relevant.