10g DISM on Solaris (SGA_MAX_SIZE & SGA_TARGET)
- From: Tony Jambu <tjambu_freelists@xxxxxxxxxxxx>
- To: Oracle-L@xxxxxxxxxxxxx
- Date: Fri, 24 Jun 2005 21:14:25 +1000
Hi
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: 10.1.0.4 (64bit)
spfile has:
SGA_MAX_SIZE=500M
SGA_TARGET=200M
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
^^^^
Semaphores:
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
http://www.webservertalk.com/archive149-2004-8-333787.html
Also Oracle's manual -
http://download-west.oracle.com/docs/html/B10812_01/appendix_e.htm#sthref830
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
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