Search notes:

Oracle: X$KQFSZ

Sizes (in bytes) of some database components, to be used to estimate data block capacity.
select
   inst_id,
   kqfszcom  component   ,
   kqfsztyp  type        ,  -- For example SWORD, UB4, SIZE_T, PTR_T etc.
   kqfszdsc  description ,
   kqfszsiz  size_in_byte,
   con_id
from
   x$kqfsz;

See also

v$type_size selects directly from x$kqfsz.
fixed tables

Index