Breaking: #88640 - Database field "sys_template.nextLevel" and TypoScript sublevel - inheritance removed 

See forge#88640

Description 

The database field nextLevel of the database table sys_template where TypoScript configuration is stored, has been removed.

The field nextLevel was introduced in TYPO3 v3.x before TypoScript could be imported from external files.

Nowadays, TypoScript conditions should be used much more instead of this nextLevel feature, which is kind of a pseudo-condition.

Impact 

The database field is removed, and not evaluated anymore in TypoScript compilation.

Requesting the database field in custom database queries will result in an SQL error.

Affected Installations 

TYPO3 installations that have sys_template records with this flag activated, or querying this database field in third-party extensions.

Migration 

Check for existing sys_template records having this flag activated by executing this SQL command:

SELECT * FROM sys_template WHERE nextLevel>0 AND deleted=0;

before updating TYPO3 Core.

Replace the sys_template record (the uid of the record is stored in the "nextLevel" field) with a condition e.g. [tree.level > 1] to add TypoScript for subpages.