journals are kept in sys_journal_field table. The max length of column value is 8,000.
However, this is just an application limitation and ServiceNow will actually allow more characters to be entered.
Any string field that is larger than varchar(255) is given the mediumtext data type. In the client, it will be represented as an HTML textarea, instead of an HTML input. The maximum length of mediumtext is 16,777,215 bytes.
Note, that this is 16,777,215 bytes and not characters. Multibyte characters require more bytes per character.
Refer to the following documentation.
https://support.servicenow.com/kb?id=kb_article_view&sysparm_article=KB0685779
And the following thread.
https://community.servicenow.com/community?id=community_question&sys_id=cab343a5dbd8dbc01dcaf3231f96...
