Oracle Database 12c -- Disable Log Writer Workers

Problem

Oracle Database 12c release introduced Log Writer workers (LGxx) background processes

You want to revert back to Oracle Database 11g behavior, that is, to disable LGWR workers 

Optionally disable adaptive log file sync mechanism introduced with Oracle Database 11g

Solution

To disable log writer worker set the hidden parameter and restart the instance:

alter system set "_use_single_log_writer"=true scope=spfile;

To disable adaptive log file sync set the hidden parameter and restart the instance:

alter system set "_use_adaptive_log_file_sync"=false scope=spfile;