The Write Ahead Log method replaced journaling in SQLite versions beginning with 3.7.0.

Using the WAL method, when new information is added to a database or edits to existing data are necessary, instead of altering the existing SQLite database, a new Page is written to the Write Ahead Log, leaving the main database unaffected. Pages are written in sequential order for efficiency. In the example above, the database engine will now read Page 2 from the WAL and not from the original database.¹

In the example above, new information is being added to Page 2. Instead of making any changes to the original database, the information is COMMITTED to the WAL file where a new Page 2 is created.

Data can grow in size to 1,000 pages (the default number) before reaching its maximum capacity, leaving the WAL as a potentially large source of information for forensic examiners.

Reference:

[1] https://for585.com/sqlitewal