We are currently running MTS and due to some bugs with MTS we are thinking of going to dedicated server. I was trying to estimate the memory overhead with the dedicated server configuration and the values from v$sysstat and v$sesstat seems to be incorrect. The database server has 4gb of memory.

Database SGA
show sga
Total System Global Area 2118164464 bytes
Fixed Size 69616 bytes
Variable Size 1462554624 bytes
Database Buffers 655360000 bytes
Redo Buffers 180224 bytes

Values from initSID.ora
db_block_buffers = 80000 (DB_BLOCK_SIZE=8192)
shared_pool_size = 872415232
large_pool_size = 536870912

Values from v$sysstat and v$sesstat.
select name ,sum(value/1024/1024) Mem_In_MB from v$sysstat
where name like '%memory%' group by name;
---------------------------------------------------------------- ----------
session pga memory 531199.958
session pga memory max 873752.614
session uga memory 496495.934
session uga memory max 8152.02377
sorts (memory) 12.7339716

select n.name,sum(s.value) from v$statname n, v$sesstat s
where n.statistic# = s.statistic# and n.name like '%memory%'
group by n.name;
--------------------------------------------- -----------------
session pga memory 930469.129
session pga memory max 2016793.41
session uga memory -849.53516
session uga memory max 4962.24219
sorts (memory) 146.436523

Also we are getting negative values for the session uga memory".

Can somebody help me with this.

Thanks in Advance.