Parameter and Command Reference > Logging Configuration Parameters > LogMaxLineLength 

Maximum characters in a log entry. The number of characters a log entry can include before it is truncated. Increase this value when you want long actions to be logged in full.
Allowed Range:
Minimum: 0
Maximum: 2000000000
Minimum: 100
Maximum: 1000000
Logging and/or LogStream
If you set this parameter in the Logging and LogStream sections, the setting in the LogStream section takes precedence for the specified log stream.