Config.idb backup size

The config.idb backup of my project is ~ 1.8Go. Any idea why this is so big ? We have about 10 000 tags and use v 8.1.24.

Did you convert from v7.9? There are left-over project resources that might need to be cleaned out. You should have support look over your shoulder in this case.

Are you storing large documents or datasets in memory tags? Those get placed in the internal DB.
Consider not doing that.

I did not convert from 7.9, I read this thread : Purging the config.idb after splitting frontend/backend and both PROJECT_CHANGES and PROJECT_RESOURCES tables are empty.

I don't, I removed all the tag providers and the size of the backup did not change.

I found that the culprit was the TAGCONFIG table. After pruning this table, the size of the config.idb went down from 1.8Go to 4Mo. Do you know the potential side effect of deleting this table ?

FWIW, 8.1.23 introduced automatic cleanup of older project-related tables (which migrated outside of the config.idb with 8.x) and auto-pruning on gateway startup. In that same release, opt-in functionality was added to prune old SQLTAG tables from the config.idb, activated via the system property ignition.tags.cleanupLegacyTagTables=true. Note that TAGCONFIG is still an active table and contains your UDT and tag definition data--not something you want to manually edit/purge by hand in most cases.