Pre-cautions to take when manipulating table structures There are some use-cases for modifying the tables manually in the database. One such, when using MySQL, is "downgrading" all cache_* tables from InnoDB to MyISAM, to get better performance.

Another use case is text fields storing data that require 4 byte encoding, instead of the normal 3 bytes. Manually this would look like:

ALTER TABLE t1 DEFAULT CHARACTER SET utf8mb4, MODIFY col1 CHAR(10) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci NOT NULL;

And then when interacting with this field ones need to issue SET NAMES 'utf8mb4' to ensure the connection passed data properly.

Is there any functionality in DBTNG to handle such odd use-cases, in part or in whole? Or will one need to handle them entirely manually? Are there any other pre-cautions one should take, to reduce the risk of future problems in this type of case.
I'm not aware of any support for either of those changes in DBTNG, it's just something you need to do manually.

Luckily that means that once you've done it there's no chance of DBTNG knowing or caring about it - everything should continue to work as you expect.