About SGA , shmmax, ISM on solaris

Sun Solaris 7 64bit oracle

Unix Kernel Parameter:
/etc/system
set shmsys:shminfo_shmmax=4294967295

Unix kernel statistics;
oracle_at_main-db1$ipcs -ma
IPC status from as of Thu Oct 24 20:23:25 CST 2002 T ID KEY MODE OWNER GROUP CREATOR CGROUP NATTCH SEGSZ CPID LPID ATIME DTIME CTIME
Shared Memory:
m 0 0x500483d0 --rw-r--r-- root root root root 1 68 305 305 6:31:42 6:31:42 6:31:42
m 101 0x41180c94 --rw-r----- oracle oinstall oracle oinstall 398 4711727104 1732 8979 20:20:00 20:20:00 8:30:38

Current database sga:
19:57:31 SQL> show sga

Total System Global Area 4711026364 bytes Fixed Size 102076 bytes
Variable Size 415678464 bytes
Database Buffers 4294967296 bytes
Redo Buffers 278528 bytes
As the document said, if the sga is larger than shmmax, oracle will allocate more than one shared memory segment,right?

But in my case, as you can see,SGA = 4.7Gb, shmmax =4GB

As the document said, oracle should allocate two shared memory segment. but from the ipcs result we can see that there is just one shared memory segment.
How can i understand it?

And some document said, to have ism enabled, shared memory segment must be in one segment, is it true?
use_ism is gone in oracle817, so how can i verify it?

Thanks.

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