I have an AWS PostgreSQL Database instance. I recently received a "DiskFull" error when attempting to write to it.

However, my "calculated" used space vs what AWS is reporting is completely different.

Following the article below: /knowledge-center/diskfull-error-rds-postgresql

Using this command: SELECT pg_size_pretty(SUM(pg_relation_size(oid))) FROM pg_class;
My table/index total size is 1.508 GB.
And, I have 5GB allocated to my DB.
However, the FreeStorageSpace metric is showing less than 12MB available.

Where is my other free space going?

I followed most of the steps outlined in the article. However, I don't have some permissions to run some of the commands--e.g. get log size. Which also seems a bit weird.