Segment size is 10 timer larger than SGA size

Experts,

When user wants to retrieve complete table data which is larger than allocated SGA.

Lets assume

SGA MAX size is 82 GB & Segment size is 800+ GB

Here segment size is 10 Times higher than SGA allocated SGA size , If so 

When the SELECT QUERY runs against that particular object and fetching full table data.,

Does it impact my SGA or PGA ? Do i need to adjust SGA Size or Complete 800 GB table data is handled by users session of the PGA.

Does it lead to Direct path read waits or no free buffer waits !

Regards,