This post is just a reflection, basically based on my last post about Adaptive Query Optimization/SQL Plan Directives. Several times we find some situations that can be solved by setting a parameter (likely a “_”) and we just proceed with an “alter system” disregarding about all the impact of this.
This is specially important when talking about “optimizer” parameters even for bugs causing ORA-600’s or performance issues… Changing those parameters in system will affect not only the SQL with the error but all SQLs in database, which may cause a really bad effect in some cases.
Ok Matheus, but what can I do?
Let’s to the obvious and generally applied methods:
Make sure that /dev/shm is mounted. You can check this by typing df -k at the command prompt. It will look something like this:
Filesystem Size Used Avail Use% Mounted on
shmfs 1G 512M 512M 50% /dev/shm
If you don’t find it then you will have to manually mount it as root user. The size should be more than MEMORY_TARGET or MEMORY_MAX_TARGET.
For example, if the MEMORY_TARGET is less than 2 GB, you should make like that:
#root: mount -t tmpfs shmfs -o size=2048m /dev/shm
I recommend you add an entry in /etc/fstab so that the mount remains persistent even after a reboot.
To make it, add the following entry in /etc/fstab:
shmfs /dev/shm tmpfs size=2048m 0 0
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We have a GoldenGate on Allow Mode running some extracts on RAC One Node Database (reading the archivelogs). And then, suddenly, the instance crashes (network lost contact to the server) and the other instance (thread) was auto started by CRS. To the database no problems: The other node redologs was used during the startup recover and every thing is ok.
The application running with Weblogic serverpool and gridlink just had a little contention and continued the operation thought the started instance. The Goldengate switch was manually made, but some sequences was lost. What we found? the sequences was in the old thread’s redologfiles. It should be backed up if fast_start_mttr_target was different to zero. Buuut, the world is not so beautiful:
raconenodedb> show parameters mttr
NAME TYPE VALUE
fast_start_mttr_target integer 0
How we solved?
Simple solution: identified the group/thread and made a cp from ASM. The copied redolog was used as archivelog on goldengate and everything was ok.
raconenodedb> select sequence#,group#,thread# from v$log where thread#=2 order by 1;
SEQUENCE# GROUP# THREAD#
---------- ---------- ----------
39636 6 2
39637 7 2
39638 8 2
39639 9 2
39640 10 2
ASMCMD> cp group_10.288.859482805 /oracle/grup10_thread2
copying +DGDATA/MYDB/ONLINELOG/group_10.288.859482805 -> /oracle/grup10_thread2
Easy like that.
Today’s post is a quick post!
Very quick post! very very quick post!
But it’s a helpful post!
Connected as sys with sysdba:
select x.ksppinm name,
decode(bitand(y.kspftctxvf, 7), 1,'MODIFIED',4,'SYSTEM_MOD','FALSE') ismod, decode(bitand(y.kspftctxvf, 2), 2, 'TRUE', 'FALSE') isadj
from sys.x$ksppi x, sys.x$ksppcv2 y
where x.inst_id = userenv('Instance')
and y.inst_id = userenv('Instance')
and x.indx + 1 = y.kspftctxpn
order by name;