Is this the right file to alter the storage tiers?
Yes. But your syntax is wrong. Why did you add **
for time retention values? If you need only time-based (e.g. 1 week):
[db]
mode = dbengine
storage tiers = 1
# Tier 0, per second data. Set to 0 for no limit.
dbengine tier 0 retention size = 0
dbengine tier 0 retention time = 7d
Just read the retention settings for details.