Not answered yet is the question: what is the impact of turning off MTS.
Using MTS has impact on other init.ora parameters too and can drastically
change the machines behaviour. How much depends especially on the number of
concurrent sessions.
- shared_pool_size: PGA of each process moves from the dedicated server
process to the shared pool when using MTS (because there is no dedicated
process and it has to be somewhere). So turning off MTS should result in a
smaller shared_pool_size because it is a waste of valuable memory unless
large_pool_size is used. How much can be queried from v$sesstat, statistic
"session pga memory".
- large_pool_size: should be set in an MTS environment so the PGA memory
moves to the large pool and not to the shared pool. This reduces
fragmentation of the shared pool that otherwise can lead to severe latch
waits on the shared pool latch and the library cache latch. So turning off
MTS should result in a large_pool_size=0 UNLESS parallel executions or
DBWR_IO_SLAVES are set since they use the large pool too.
- processes: is normally much lower in a MTS setup but the impact on the
SGA size is not so drastic.
- Why is MTS introduced in your environment? Main reason to use MTS is when
there are many concurrent sessions (> 150). Memory usage can be reduced and
there are much less processes running, reducing the number of context
switches. They take relatively much system CPU time and occur when a process
takes the CPU or releases it again. A large process run queue ("sar -q") can
be the result when many processes are fighting to get a CPU time slice. The
system spends to much on CPU system time that could better be spend on CPU
user time.
Turning MTS off can have big (negative) impact on the machines behaviour but
it all depends on the available memory, the number of processes (=
concurrent sessions) and the number of CPU's in the machine. On the other
hand: when MTS is turned on for no good reason (say < 50 concurrent
sessions) the overhead costs more than what it saves.
MT <mtechera_at_wpmc.com> schreef in berichtnieuws
am50lt$kes$1_at_news.online.de...
| Thank you for the help Richard and Kenneth!
|
| I was able to confirm that MTS is on, as you suggested but
| unfortunately it is not clear if it is necessary or not
| for it to remain turned on
| (I am playing the role of an assistant here).
|
|
| One follow up question:
|
| Is there any way to determine if any of the current session are
| coming from the MTS dispatcher by looking at some of the
| DBA_ views? Or would this have to be done by looking at the OS processes?
|
| Thanks again!
|
| Mario
|
|
|
| <kennethkoenraadt_at_no-spam.hotmail.com> wrote in message
news:3d85f807.613111_at_news.mobilixnet.dk...
| > On Tue, 17 Sep 2002 00:44:53 +1000, "Richard Foote"
| > <richard.foote_at_bigpond.com> wrote:
| >
| > >
| > >"MT" <mtechera_at_wpmc.com> wrote in message
| > >news:am4pgn$g14$1_at_news.online.de...
| > >> Hello All:
| > >>
| > >>
| > >> Ora 8.1.7 AIX
| > >>
| > >> What is the easiest way to tell if MTS is turned on?
| > select DECODE ( value,0, 'MTS is OFF', 'MTS is ON')
| > from v$parameter where name = 'mts_servers';
| >
| > >
| > >MTS_DISPATCHERS is the key parameter that "turns on" MTS.
| >
| > AND parameter MTS_SERVERS (must be > 0).
| > >
| > >You could also look at the services for the listener(s) for the
database to
| > >see if dispatchers have been registered.
| > >
| > >You could also look at V$CIRCUITS to see how many connections have been
made
| > >via dispatchers. V$DISPATCHER, V$DISPATCHER_RATE, V$MTS and
V$SHARED_SERVER
| > >(among others) all gives you useful information.
| > >
| > >>
| > >> How can it be turned off?
| > >
| >
| > >Comment out the MTS_DISPATCHERS and it's turned off. No dispatchers, no
MTS.
| > >
| > OR (to disable MTS immediately without restarting the instance ):
| >
| > "alter system set MTS_SERVERS = 0"
| > >>
| > >> Is there any risk in turning off?
| > >
| > >If the reason you have MTS turned on is so that you can handle the 5000
| > >connections required to the database, then turning it off will have a
rather
| > >unfortunate consequence (as these connections will now each demand
their own
| > >dedicated connection, and the resource overheads this entails).
| > >
| > >Before turning it off, you need to ask why it was turned on in the
first
| > >place, and can a dedicated configuration handle the required dedicated
load.
| > >
| > >Note also that "features" such as connection manager and IIOP
connections
| > >require MTS to be configured at the backend so you may need to suss
this out
| > >as well.
| > >
| > >Cheers
| > >
| > >Richard
| > >
| > >>
| > >> Thanks,
| > >> Mario
| > >>
| > >>
| > >
| > >
| >
| > - Kenneth Koenraadt
|
|
Received on Mon Sep 16 2002 - 15:45:04 CDT
