There are 3 places where that value is set:
- 2 configure.php files: DIR_FS_SQL_CACHE
- configuration table in database SESSION_WRITE_DIRECTORY

If you're encountering PHP errors that are showing that the system is trying to write session or cache data to some invalid path, then one of those 3 settings contains incorrect data.
And, if you've checked all those 3 settings, then either you're not looking at the data actually ON the server, or you're looking in the wrong database or wrong table. Remember, if your site is set up to use table prefixes (DB_PREFIX other than '') then you need to look at the table whose name starts with that prefix.