I recently upgraded by OVM to 3.4.3(.1511), but now my Oracle Enterprise Linux 6.9 PVM guests won’t start up any more. They don’t finish the ‘Starting automount’ in the boot / startup screen. It does not fail, it just won’t continue.
There is nothing special in the /etc/fstab I guess… : Continue reading
In this blog post I will describe a few cases with extended (distance) Oracle clusters using examples with different storage, controller, failgroup configurations and where you have data blocks you left when failure happens. Continue reading
First of all, both terms ‘extended’ and ‘stretched’ are used on blogs, in documentation and logfiles. I will use ‘extended’ in this one. Also, voting files are files, not disks. Oracle will store the file(s) on one of the disks within the specified diskgroup, preferable in different failgroups. Also people talk about a ‘RAC’ cluster, but an Oracle cluster can exist without RAC. RAC is the database option to run the database in a cluster on Oracle clusterware.
Sorry, no images in this blog post… only text.
It’s not distance. Oracle does not know if it’s in the same or different racks or buildings, divided by roads or rivers… There is no setting ‘extended=Y’ in Oracle that it knows about being extended.
It’s the way _you_ design the storage for Oracle clusterware and ASM.
My point of view, extended is; When there is mirroring of blocks on disks and these mirrored blocks are on disks in different storage locations. Continue reading
Yes, enabling the Oracle 12c direct NFS client on Windows and it is documented, but I didn’t get changed on Oracle Support (I have send an improvement request for Doc ID 1468114.1)…
One needs to run ‘%ORACLE_HOME%\bin\enable_dnfs.bat’ now, which does NOT copy the ‘oranfsodm12.dll’ over the ‘oraodm12.dll’, but it copies the ‘oranfsodm12.dll’ to the ‘%ORACLE_HOME%\rdbms\lib\odm\’ directory!
After the file has been copied and Oracle is restarted, the [Oracle instance running with ODM: Oracle Direct NFS ODM Library Version 3.0] line in the alert.log is shown!
Oracle Database Installation Guide for Microsoft Windows – Oracle Database Postinstallation Tasks – 7.5.1.5 Enabling Direct NFS Client: http://docs.oracle.com/database/121/NTDBI/postcfg.htm#CHDFGFDC
ps. on Windows the supported ‘nfs_version’ is still NFSv3 :(
When queries, with a lot of data being send or received, like in ETL or data (up)loads (a la swingbench), suddenly get disconnected, it might be a network issue. There might be no error, or sometimes an ORA-12592…
Ok, I added a new disk (well old actually, but new for the machine) to my Oracle VM server. It discovered it (or do it manually) and I wanted to create a new repository on it. Unfortunately it came with the following error:
Server error: 'The backing device /dev/mapper/3500a075109146bee is not allowed to contain partitions'
Let’s get an endpoint_value for a hight-balanced histogram which represents a date:
select table_name, column_name, endpoint_number, endpoint_value, endpoint_actual_value from dba_tab_histograms where table_name='BSLN_BASELINES' and column_name='LAST_COMPUTE_DATE' order by endpoint_number;
Endpoint values for dates will be shown as followed: ‘2457594.23701157’.
The number in front of the dot is the day’s since ’01 JAN -4712′, this is retrievable with the Julian format element ‘J’:
select to_char(to_timestamp('2457594', 'J'), 'DD MON YYYY') endpoint_actual_value from dual; -- 24 JUL 2016
select to_char(to_timestamp('1', 'J'), 'DD MON SYYYY') endpoint_actual_value from dual; -- 01 JAN -4712
select to_char(to_timestamp('5373484', 'J'), 'DD MON YYYY') endpoint_actual_value from dual; -- 31 DEC 9999
The number after the dot is the faction of the day: .5 is noon, 0.25 is six ‘o clock in the morning:
select to_char(trunc(sysdate) + 0.25, 'HH24:MI:SS') endpoint_actual_value from dual; -- 06:00:00 select to_char(trunc(sysdate) + 0.23701157, 'HH24:MI:SS') endpoint_actual_value from dual; -- 05:41:18 select to_char(trunc(sysdate) + 0.87305213, 'HH24:MI:SS') endpoint_actual_value from dual; -- 20:57:12
&tldr; in sqlnet.ora :
# the minimum allowed client version to connect to the databases from this home # set this to accept lower versions of the autentication protocol SQLNET.ALLOWED_LOGON_VERSION_SERVER=11 # if you have a database link to a lower version of an Oracle # set this to that lower version to talk the same authentication protocol # 12a => 12.1.0.2 # SQLNET.ALLOWED_LOGON_VERSION_CLIENT=12a # 12a for Oracle Database 12c release 12.1.0.2 or later # 12 for the critical patch updates CPUOct2012 and later Oracle Database 11g # 11 for Oracle Database 11g # 10 for Oracle Database 10g # 9 for Oracle9i # 8 for Oracle8i
Ah, an old client is trying to connect to Oracle 12c (presumably)… ;)
Also “ORA-03134: Connections to this server version are no longer supported” can occur.
This actually implies that the authentication protocols use between client and server do not match. In Oracle 12c, the authentication protocol uses SHA-2 encryption algorithm by default, where older clients use SHA-1. So when an older client is used with defaults, the server will not accept the connection.
The best option would be upgrading the client, but when older dll’s are used (like ojdbc14.jar and you can not change this), this is a problem. The database instance can be told to accept older clients and use the older SHA-1 encryption algorithm.
When you run Oracle Grid 12c ‘cluvfy stage -pre crsinst’ on Linux 7 (Oracle Enterprise Linux 7.2 in my case) you will get the following error:
Starting check for /dev/shm mounted as temporary file system ... ERROR: PRVE-0421 : No entry exists in /etc/fstab for mounting /dev/shm PRVE-0421 : No entry exists in /etc/fstab for mounting /dev/shm PRVE-0421 : No entry exists in /etc/fstab for mounting /dev/shm PRVE-0421 : No entry exists in /etc/fstab for mounting /dev/shm Check for /dev/shm mounted as temporary file system failed
When you do a ‘df -h’ you will see that ‘/dev/shm’ actually is mounted:
Filesystem Size Used Avail Use% Mounted on devtmpfs 24G 0 24G 0% /dev tmpfs 24G 0 24G 0% /dev/shm
This is due to a bug (Doc ID 2065603.1) which comes from the case that the cluvfy check does not check the actual mount of the file system, but looks for the persistence line of this mount in ‘/etc/fstab’ like it did in Linux 6. In Linux 7 you get this tmpfs mount by default.
Goal: To add new larger disk to LVM, move data and remove old smaller one
When using Oracle VM in my work, a disk can be enlarged in Oracle VM manager for a virtual machine. But because of an internal loop-mount on the XEN hypervisor level, the disk-file which is presented to the virtual machine as a disk, is not able to ‘pass on’ it’s resize information to the OS. This requires an unmount and mount of the disk-file on hypervisor level, or in simple words: a reboot of the virtual machine… yikes! Continue reading