Shared Sever Mode and Total No of Connections ?

Question

Hello,
Env:Ora 10g on Win2003
The DB is in Shared Server Mode (yes, the application connects with SERVER=SHARED).
During peak hour i could see around 80 connections in v$session from the this username with server = shared.
The count of shared servers in v$shared_server too was around 80+ at that time.
The v$license said the SESSIONS_HIGHWATER as around 85
Is there any way to find out, how many connections would have been there if the connections were DEDICATED ?
TIA,
JJ

Answer 1

J..J wrote:
The DB is in Shared Server Mode (yes, the application connects with SERVER=SHARED).First of all, the fact that the application connects with SERVER=SHARED does not indicate that the DB instance is configured with Shared Server parameters. You need to check and confirm that the instance is setup for Shared Server Mode?
SQL> show parameters shared_server
NAME                                 TYPE        VALUE
max_shared_servers                   integer     5
shared_server_sessions               integer
shared_servers                       integer     1
SQL> show parameters dispatcher
NAME                                 TYPE        VALUE
dispatchers                          string      (PROTOCOL=TCP)(DISPATCHERS=1)(
                                                 LISTENER=LISTENER_TESTDB01)
max_dispatchers                      integer
SQL> show parameters circuit
NAME                                 TYPE        VALUE
circuits                             integer
SQL>One thing to understand is that in any mode (Shared Server or Dedicated), the number of sessions will always be around the connected sessions. Where you see a difference between the two is in the number of server processes created for each mode for those number of sessions. Shared Server mode will create less number of Server processes than dedicated mode.
Here is a quick test check v$process and count number of processes from OS against number of sessions for each mode.
-- Connect 20 sessions with SERVER=SHARED
testdb01@dbmsdirect1:/export/home/oracle:ps -ef|grep testdb0101|grep -v grep|wc -l
      17
testdb01@dbmsdirect1:/export/home/oracle:
SQL> select count(1) from v$session;
  COUNT(1)
        35
SQL> select count(1) from v$process;
  COUNT(1)
        18
SQL>
SQL>  select * from v$shared_server ;
NAME PADDR            STATUS             MESSAGES      BYTES     BREAKS CIRCUIT                IDLE    BUSY      REQUESTS
S000 000000039F25A200 EXEC                   1359     289845          6 000000039C711D50     197651     130           618
SQL>
SQL> select * from v$shared_server_monitor;
MAXIMUM_CONNECTIONS MAXIMUM_SESSIONS SERVERS_STARTED SERVERS_TERMINATED SERVERS_HIGHWATER
                 21               21               3                  3                 3
SQL>
-- Exist 19 sessions out of 20 Sessions
testdb01@dbmsdirect1:/export/home/oracle:ps -ef|grep testdb0101|grep -v grep|wc -l
      17
testdb01@dbmsdirect1:/export/home/oracle:
SQL> select count(1) from v$session;
  COUNT(1)
        16
SQL> select count(1) from v$process;
  COUNT(1)
        18
-- Exit remaining 1 session and  Connect 20 all sessions with SERVER=DEDICATED
testdb01@dbmsdirect1:/export/home/oracle:ps -ef|grep testdb0101|grep -v grep|wc -l
      38
testdb01@dbmsdirect1:/export/home/oracle:
SQL> select count(1) from v$session;
  COUNT(1)
        36
SQL> select count(1) from v$process;
  COUNT(1)
        38
SQL>
SQL> select * from v$shared_server ;
NAME PADDR            STATUS             MESSAGES      BYTES     BREAKS CIRCUIT                IDLE    BUSY      REQUESTS
S000 000000039F25A200 WAIT(COMMON)           1374     291630          7 00                   243613     149           618
SQL>
SQL>
SQL>  select * from v$shared_server_monitor;
MAXIMUM_CONNECTIONS MAXIMUM_SESSIONS SERVERS_STARTED SERVERS_TERMINATED SERVERS_HIGHWATER
                 21               21              11                 11                 3
SQL>
Notice the difference in the number of server processes created by each mode