What does a high gc current block busy event value indicate?

What does a high gc current block busy event value indicate?

A.
Access to cached data blocks was delayed because they were busy either in the remote or the
local cache.

B.
A large number of requested blocks were not cached In any instance.

C.
Asynchronous input/output (I/O) is disabled.

D.
Delay in processing has occurred In the GCS, caused by CPU saturation and would have to be
solved by additional CPUs and load-balancing.

Explanation:
The gc current block busy wait event indicates that the access to cached data
blocks was delayed because they were busy either in the remote or the local cache. This could be
caused by any of the following:
Oracle Real Application Clusters Administration and Deployment Guide