How to Speed up and Troubleshooting MRP (Log Apply Rate of a Standby Database) Stuck Issues

To Speed up MRP on Standby database, Check for

1) parallel_execution_message_size - this is an OS dependent parameter
2) recovery_parallelism - this will be dictated by the numbers of CPU's and your ability to handle IO
3) Consider increasing sga_target parameter, if it's set to low.
4) Check for Disk I/O. Move you I/O intensive files to faster disks including Online Redo log and Standby redo log files.

I've came across below these links, which I've found very useful in this regards,

http://emrebaransel.blogspot.in/2010/06/mrp-speed-log-apply-rate-of-standby.html

How to resolve MRP stuck issues on a physical standby database? (Doc ID 1221163.1)

Steps to perform for Rolling forward a standby database using RMAN Incremental Backup. (Doc ID 836986.1)