Single row INSERT do many many blocks read!

Hi all,

    We have migrated 10T data use sql*loader. Then there need twenty seconds for responsing of insert one rows. We trace insert operation with 10046 and find the operation of inserting one rows need access thousands of blocks .  We have find one document  "INSERT slow on ASSm (document 1263496.1)"  match our issue.  So we have the following question:

1、which batch insert operation will resulting in that issue?

2、We have set pctfree is 10,why all block have not free space?

Thanks & Regards

Ryan