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10g DISM on Solaris

From: Tony Jambu <>
Date: Fri, 24 Jun 2005 21:05:52 +1000
Message-Id: <>


Am trying to setup Oracle's Automatic Shared Memory Mgmt (ASMM) on Solaris 9 (and 10) and having some issues. Not sure if it is
(i) bug with Oracle
(ii) bug with Solaris 9,
(iii) I screwed up or
(iv) my understanding/assumption is wrong

O/S: Solaris 9(SPARC)
Oracle: (64bit)

spfile has:


I thought that with the above, oracle will startup with 200M SGA and _only_ 200M of System memory is allocated. You then have the ability to dynamically increase it (using ALTER SYSTEM SET sga_target=xxx ) up to SGA_MAX_SIZE. Q. Is the above assumption correct?

Some stats and information

# -------------------------------------

# Get Memory Information from Oracle
# -------------------------------------

% sysresv OEM10G

IPC Resources for ORACLE_SID "OEM10G" :
Shared Memory:

ID              KEY
7040            0x629dc97c



ID              KEY
4718614         0xdf751d7c

Oracle Instance alive for sid "OEM10G"
# -------------------------------------

# Get Memory allocated to Oracle
# -------------------------------------
% ipcs -a | grep 7040
m       7040   0x629dc97c --rw-r-----   oracle      dba   oracle      dba     18  524296192 19547 23979 15:22:46 15:22:46 14:59:24
       ^^^^                                                                      ^^^^^^^^^

Notice that it has allocated 500M of memory. I was expecting it to be 200M

% ps -ef | grep dism

    root 23069 1 0 14:59:25 ? 0:00 ora_dism_OEM10G

THis shows Oracle's DISM is running.

Q1. When you set SGA_MAX_SIZE=500M and SGA_TARGET_SIZE=200M,

     on startup does Solaris allocate 200M or 500M?

# ==========================

# More information
# ==========================

SQL> show sga

Total System Global Area 524288000 bytes

Fixed Size                  1303456 bytes
Variable Size             388242528 bytes
Database Buffers          134217728 bytes
Redo Buffers                 524288 bytes

SQL> show parameter sga

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
lock_sga                             boolean     FALSE
pre_page_sga                         boolean     FALSE
sga_max_size                         big integer 500M
sga_target                           big integer 200M

Q2.  Does setting SGA_MAX_SIZE make the Shared Memory non-pagable?
        see reply from Howard Rogers & Nuno
        Also Oracle's manual -
        Intimate Shared Memory   

On Solaris systems, Oracle Database uses Intimate Shared Memory (ISM) for shared memory segments because it shares virtual memory resources between Oracle processes. ISM causes the physical memory for the entire shared memory segment to be locked automatically. On Solaris 8 and Solaris 9 systems, dynamic/pageable ISM (DISM) is available. This enables Oracle Database to share virtual memory resources between processes sharing the segment, and at the same time, enables memory paging. The operating system does not have to lock down physical memory for the entire shared memory segment.

Q3. How does one proof or disproof that Solaris has Dynamic memory allocation enabled?         

PS: System has been patch and read the following refernece Enabling Dynamic SGA on Solaris platform - Doc ID: 151222.1 SUN bug. 4675878

Received on Fri Jun 24 2005 - 07:11:10 CDT

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