Controlfile Sequential Read/ Parallel Write

'controlfile sequential read' occurs while reading control file (backup, share information from controlfile between instances etc). The parameters in V$session_wait are as follows,

P1 - The file# of control file from which the session is reading.
P2 – The block# from which the session starts reading.
P3 – The no. of blocks the session is trying to read.

'controlfile parallel write' occurs while writing to all the control files. The parameters in V$session_wait are as follows,

P1 – No. of control files being updated.
P2 – No. of blocks that are being updated.
P3 – No. of IO requests.

Tuning Options: Use Asynchronous IO if possible. Move the controlfile to a different disk or use faster disk.

Thanks