V$TYPE_SIZE

V$TYPE_SIZE displays the sizes of various database components for use in estimating data block capacity.

Column	Datatype	Description
`COMPONENT`	`VARCHAR2(8)`	Component name, such as segment or buffer header
`TYPE`	`VARCHAR2(8)`	Component type
`DESCRIPTION`	`VARCHAR2(32)`	Description of the component
`TYPE_SIZE`	`NUMBER`	Size of the component