Does the PCI require to protect the Credit Card Info in the transaction log?
This means text logs, such as those from Log4net. 
Not database redo/undo/transaction files

Why?

PCI says that Credit card numbers (PAN) should be sent and stored as encrypted in the database, which means only the encrypted value will appear in any database log file (whether an error log or the actual redo/undo/transaction log file). See Page 8 and item 3.4 of your document for this.

Edit, after @Shark's observation


The database doesn't do encryption/decryption: only storage, no processing
The sending/receiving application does encryption/decryption: only processing, no storage