Tales From A Lazy Fat DBA

Today while working on one of my practice machine, I’ve started receiving error when tried to start-up one of the instance which is on Cooked File system. Error reads about MEMORY_TARGET.  To be precise about the error message and code, below is what i was getting second ago.

SQL> startup
ORA-00845: MEMORY_TARGET not supported on this system

Below are the steps in sequence what i performed to test and mitigate the error.

1. I’ve checked the pfile of the instance to check MEMORY_TARGET entires and values to discover if there is any problem with the values assigned (I have the AMM enabled in my machine)
*.memory_target=715128832

2. Then i’ve checked error details more closely using OERR utlity to find the cause of the problem and suggestions.

[oracle@localhost dbs]$ oerr ORA 845
00845, 00000, “MEMORY_TARGET not supported on this system”
// *Cause: The MEMORY_TARGET parameter was not supported on this operating system or /dev/shm was not sized correctly on Linux.
// *Action: Refer to documentation for a list of supported operating systems. Or, size /dev/shm to be at least the SGA_MAX_SIZE on each Oracle instance running on the system.

Error clearly points towards the /dev/shm size on OS and asking to set the size of it to atleast SGA_MAX_SIZE on instance running which is 684m.

3. Now when we have the Cause in hand let’s try to fix the problem.

let me check current settings.

[oracle@localhost dbs]$ df -h
Filesystem            Size    Used       Avail            Use%        Mounted on
/dev/mapper/VolGroup00-LogVol00
30G   23G        6.0G            80%         /
/dev/sda1              99M   55M       40M            58%          /boot
tmpfs                 664M  154M   510M         24%        /dev/shm        /*tmps (Temp File Storage area) is in MB’s – CAUSE CLEARED*/

And it’s 664M which is clearly below the SGA_MAX_SIZE = 684m

Some more checks:
[root@localhost ~]# more /etc/fstab
/dev/VolGroup00/LogVol00 /                       ext3    defaults        1 1
LABEL=/boot             /boot                   ext3    defaults        1 2
tmpfs                   /dev/shm                tmpfs   defaults        0 0
devpts                  /dev/pts                devpts  gid=5,mode=620  0 0
sysfs                   /sys                    sysfs   defaults        0 0
proc                    /proc                   proc    defaults        0 0
/dev/VolGroup00/LogVol01 swap                    swap    defaults        0 0

4. Let’s try to add up some memory space to tmpfs area.
I’ve added exact 1GB to /etc/fstab entry. Let me check the change

[root@localhost ~]# vi /etc/fstab

[root@localhost ~]# more /etc/fstab
/dev/VolGroup00/LogVol00 /                       ext3    defaults        1 1
LABEL=/boot             /boot                   ext3    defaults        1 2
tmpfs                   /dev/shm                tmpfs   defaults,size=1G        0 0
devpts                  /dev/pts                devpts  gid=5,mode=620  0 0
sysfs                   /sys                    sysfs   defaults        0 0
proc                    /proc                   proc    defaults        0 0
/dev/VolGroup00/LogVol01 swap                    swap    defaults        0 0

Alrighty, to fix the settings/changes let’s remount /dev/shm

[root@localhost ~]# mount -o remount /dev/shm
[root@localhost ~]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/VolGroup00-LogVol00
30G   23G  6.0G  80% /
/dev/sda1              99M   55M   40M  58% /boot
tmpfs                 1.0G  154M  4.9G   4% /dev/shm

D.O.N.E

5. Now we are done with the change, let’s try to start the instance once again.

[oracle@localhost ~]$ . oraenv
ORACLE_SID = [orcl] ? orcl
The Oracle base for ORACLE_HOME=/u01/app/oracle/product/11.2.0/dbhome_2 is /u01/app/oracle

SQL> startup
ORACLE instance started.

Total System Global Area  715616256 bytes
Fixed Size                  1338924 bytes
Variable Size             482345428 bytes
Database Buffers          226492416 bytes
Redo Buffers                5439488 bytes
Database mounted.
Database opened.

It’s UP!!