Oracle change initialization parameter with "deferred" keyword The description of deferred and scope keyword is listed below (extracted from Oracle documentation). The meaning of them gives me an indication that deferred can just use the memory scope. Is my understanding right? Thanks.

DEFERRED
The DEFERRED keyword sets or modifies the value of the
parameter for future sessions that connect to the database. Current
sessions retain the old value.
SCOPE
The SCOPE clause lets you specify when the change takes effect.
Scope depends on whether you started up the database using a
traditional plain-text parameter file (pfile) or server parameter file
(spfile).
MEMORY indicates that the change is made in memory, takes effect
immediately, and persists until the database is shut down. If you
started up the database using a parameter file (pfile), then this is
the only scope you can specify.
SPFILE indicates that the change is made in the server parameter
file. The new setting takes effect when the database is next shut down
and started up again. You must specify SPFILE when changing the value
of a static parameter that is described as not modifiable in Oracle
Database Reference.
BOTH indicates that the change is made in memory and in the server
parameter file. The new setting takes effect immediately and persists
after the database is shut down and started up again.
If a server parameter file was used to start up the database, then
BOTH is the default. If a parameter file was used to start up the
database, then MEMORY is the default, as well as the only scope you
can specify.
I've checked experimentally (Oracle 11.1) that actually ALTER SYSTEM ... DEFERRED SCOPE=SPFILE is allowed, although it seems to me that DEFERRED is ignored in this context. Also SCOPE=BOTH and SCOPE=MEMORY are allowed, obviously. 

What you cannot do (the manual that you quote overlooked it) is ALTER SYSTEM ... DEFERRED on the parameter that has (V$PARAMETER.ISSYS_MODIFIABLE, V$PARAMETER.ISSES_MODIFIABLE) = (IMMEDIATE, FALSE). This results in:

ORA-02096: specified initialization parameter is not modifiable with this option