Search notes:

Oracle: X$KSMFSV

Names of variables, address of their value in the SGA, their datatype and size of the datatype.

select   
-- addr addr_hex,
-- to_number(addr    , rpad('x', 16, 'x')) addr,
   ksmfsnam                                variable_name,
   to_number(ksmfsadr, rpad('x', 16, 'x')) address,
   ksmfstyp                                typ,
   ksmfssiz                                siz
from
   x$ksmfsv
order by
   variable_name
;

SCN number (kcsgscn_)

Such a variable is for example kcsgscn_ which stores the current SCN number:

select
   to_number(mem.ksmmmval, rpad('x', 16, 'x'))      value,
   vdb.current_scn 
from
   x$ksmfsv   var                                   join
   x$ksmmem   mem on var.ksmfsadr = mem.addr cross  join
   v$database vdb 
where
   var.ksmfsnam = 'kcsgscn_' -- SCN Number  
;

Latches

Many of these variables seem to store the address of latches which are exposed in x$kslld or x$kslltr.

select   
-- addr addr_hex,
-- to_number(addr    , rpad('x', 16, 'x')) addr,
   ksmfsnam                                variable_name,
   lld.kslldnam                            lld_name,
   lld.ksllddsp                            lld_description,   
   llt.kslltnam                            llt_name,
   to_number(ksmfsadr, rpad('x', 16, 'x')) address,
   ksmfstyp                                typ,
   ksmfssiz                                siz
from
   x$ksmfsv        var                                    left join
   x$kslld         lld on  var.ksmfsadr = lld.kslldadr    left join
   x$kslltr        llt on  var.ksmfsadr = llt.kslltaddr
where
   coalesce(lld.kslldadr, llt.kslltaddr) is not null
;

Unix Epoch

ksudbrmseccnt_ stores the value of the Unix epoch (seconds since January 1st 1970):

select
   date '1970-01-01' + (1/24/60/60) * to_number(mem.ksmmmval, rpad('x', 16, 'x')) as "current time UTC"
from
   x$ksmfsv   var                                   join
   x$ksmmem   mem on var.ksmfsadr = mem.addr
where
   var.ksmfsnam = 'ksudbrmseccnt_'
;

Dumping variable values with oradebug

ORADEBUG allows to print the value of a variable with the dumpvar command:

oradebug dumpvar kcsgscn

Column ksmfstyp

ksmfstyp shows the type of the variable: Some of these types are basic memory units such as uword, ub4, int etc., others seem to refer to some kind of structs, such as ksllt, ksbsa, kzxctok etc. Also seen is void *, size_t, oratext * and many more.

In the case of the type being ksllt, it can be joined to x$kslld to list variables that are related to latches.