You see following ORA-00600 error in ST22 dump or alert.log.
ORA-00600: internal error code, arguments: [qkaffsindex1],
, , , , , , , , , , 
When you look into the relevant dev trace of the dump or
incident trace file referred in alert.log, you see the error happens when
running SQL statement like
“delete from <table name> where ..”.
This issue is addressed as an oracle bug 19438874 which
happens in oracle release 11.2 to 12.1. It is fixed in future release 12.2.
The bug fix has been delivered in following SBP version.
SBP 126.96.36.199.14 201505
SBP 188.8.131.52.6 201505
SBP 184.108.40.206.3 20505
Install the above SBP to fix the error.
As a workaround, you can set parameter “_fast_full_scan_enabled”
to FALSE. But this is not a recommended way.