How do you use B-Tree?

What is caching Ref Tbls in Buffer Pool keep

How do you configure sort_area_size

what is the alternate for sorting and group by..

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comment on the below::

SQL> show parameters buffer

NAME TYPE VALUE
------------------------------------ ------- ------------------------------
buffer_pool_keep string
buffer_pool_recycle string
db_block_buffers integer 7500
log_buffer integer 163840
use_indirect_data_buffers boolean FALSE
SQL> show parameters sort

NAME TYPE VALUE
------------------------------------ ------- ------------------------------
nls_sort string
sort_area_retained_size integer 131072
sort_area_size integer 131072
sort_multiblock_read_count integer 2

Suggestions, welcome .. Thx.