vlan configuration on cisco switch Catalyst 6500 Series

August 9th, 2012

Firstly, have a read of vlan wiki page(benefits compared to physical lan, cisco VTP):


Then, have a read of the following about configuration of vlan on cisco switch Catalyst 6500 Series(vlan ranges, vlan translation):


resolved – semget failed with status 28 failed oracle database starting up

August 2nd, 2012

Today we met a problem with semaphore and unable to start oracle instances. Here's the error message:

ORA-27154: post/wait create failed
ORA-27300: OS system dependent operation:semget failed with status: 28
ORA-27301: OS failure message: No space left on device
ORA-27302: failure occurred at: sskgpcreates

So it turns out, the max number of arrays have been reached:
#check limits of all IPC
root@doxer# ipcs -al

------ Shared Memory Limits --------
max number of segments = 4096
max seg size (kbytes) = 67108864
max total shared memory (kbytes) = 17179869184
min seg size (bytes) = 1

------ Semaphore Limits --------
max number of arrays = 128
max semaphores per array = 250
max semaphores system wide = 1024000
max ops per semop call = 100
semaphore max value = 32767

------ Messages: Limits --------
max queues system wide = 16
max size of message (bytes) = 65536
default max size of queue (bytes) = 65536

#check summary of semaphores
root@doxer# ipcs -su

------ Semaphore Status --------
used arrays = 127
allocated semaphores = 16890

To resolve this, we need increase value of max number of semaphore arrays:

root@doxer# cat /proc/sys/kernel/sem
250 1024000 100 128
                 ^---needs to be increased


Here's an example with toilets that describes differences between mutex and semaphore LOL http://koti.mbnet.fi/niclasw/MutexSemaphore.html

thin provisioning aka virtual provisioning on EMC Symmetrix

July 28th, 2012

For basic information about thin provisioning, here's some excerpts from wikipedia/HDS site:

Thin provisioning is the act of using virtualization technology to give the appearance of more physical resource than is actually available. It relies on on-demand allocation of blocks of data versus the traditional method of allocating all the blocks up front. This methodology eliminates almost all whitespace which helps avoid the poor utilization rates, often as low as 10%, that occur in the traditional storage allocation method where large pools of storage capacity are allocated to individual servers but remain unused (not written to). This traditional model is often called "fat" or "thick" provisioning.

Thin provisioning simplifies application storage provisioning by allowing administrators to draw from a central virtual pool without immediately adding physical disks. When an application requires more storage capacity, the storage system automatically allocates the necessary physical storage. This just-in-time method of provisioning decouples the provisioning of storage to an application from the physical addition of capacity to the storage system.

The term thin provisioning is applied to disk later in this article, but could refer to an allocation scheme for any resource. For example, real memory in a computer is typically thin provisioned to running tasks with some form of address translation technology doing the virtualization. Each task believes that it has real memory allocated. The sum of the allocated virtual memory assigned to tasks is typically greater than the total of real memory.

The following article below shows the step how to create thin pool, add and remove components from the pool and how to delete thin pool:


And for more information about thin provisioning on EMC Symmetrix V-Max  with Veritas Storage Foundation, the following PDF file may help you.

EMC Symmetrix V-Max with Veritas Storage Foundation.pdf


1.symcfg -sid 1234 list -datadev #list all TDAT devices(thin data devices which consists thin pool, and thin pool provide the actual physical storage to thin devices)
2.symcfg -sid 1234 list -tdev #list all TDEV devices(thin devices)

3.The following article may be useful for you if you encountered problems when trying to perform storage reclamation(VxVM vxdg ERROR V-5-1-16063 Disk d1 is used by one or more subdisks which are pending to be reclaimed):




Categories: Hardware, SAN, Storage Tags: ,

oracle RMAN backups and hot backup mode

July 28th, 2012

In one sentence, to backup Oracle with OS(BCV for example), database should be put into hot backup mode. But RMAN backups can be performed while the database is online.

Also, oracle GoldenGate is used to replicate DB between heterogeneous systems, for example, oracle replicated to mysql/sql server etc.

oracle golden gate documentation

July 28th, 2012

Here's some excerpts from oracle document about oracle golden gate:

Robust Modular Architecture

The Oracle GoldenGate software architecture is comprised of three primary components:
Capture, Trail Files, and Delivery. This modular approach allows each component to perform
its tasks independently of the others, accelerating data replication and ensuring data integrity.
Figure 1: Oracle GoldenGate leverages a component-based architecture to optimize real-time
information access and availability.

  • Capture

Oracle GoldenGate’s Capture module resides on the source database and looks for new
transactional activity. The Capture module reads the result of insert, update, and delete
operations by directly accessing the database transaction (redo) logs, and then immediately
captures new and changed data for distribution.
The Capture module only moves committed transactions—filtering out intermediate activities
and rolled-back operations—which not only reduces infrastructure load but also eliminates
potential data inconsistencies. Further optimization is achieved through transaction grouping
and optional compression features.
Oracle GoldenGate 11g can also capture messages from JMS messaging systems to deliver to
heterogeneous databases in real time for scalable and reliable data distribution.

  • Trail Files

Oracle GoldenGate’s Trail Files contain the database operations for the changed data in a
transportable, platform-independent data format. Trail Files are a critical component within
Oracle GoldenGate’s optimized queuing mechanism. They reside on the source and/or target
server but exist outside of the database to ensure heterogeneity, improved reliability, and
minimal data loss. This architecture minimizes impact to the source system because no
additional tables or queries to the database are required to support the data capture process.
The Capture module reads once, and then immediately moves the captured data to the external
Trail File for delivery to the target(s).
In the event of an outage at the source and/or target, the Trail Files contain the most-recent
data up to the point of the outage, and the data is applied once the systems are online again.

  • Delivery

Oracle GoldenGate’s Delivery module takes the changed data from the latest Trail File and
applies it to the target database using native SQL for the appropriate relational database
management system. Delivery can be made to any open database connectivity–compliant
database. The Delivery module applies each transaction in the same order as it was committed
and within the same transactional context as at the source, enabling consistency and referential
integrity at the target. To enhance IT flexibility, captured data can also be delivered to a Java
Message Service destination or as a flat file using Oracle GoldenGate Application Adapters.

For full documentation, you can refer to the following pdf file: http://www.oracle.com/us/products/middleware/data-integration/goldengate11g-ds-168062.pdf?ssSourceSiteId=otnen

IT solutions I can think of now

July 26th, 2012

1.Configuration Management and Data Warehouse

     BMC ControlM, Symantec Altiris, Aperture, CMDB

     spacewalk, pulp, puppet. cfengine, chef

     Oracle Exalytics, SAP HANA
     vmware, citrix, openvz, xen, kvm, cdn(such as cloudflare), cloudstack, openstack, openshift, CloudFoundry, hadoop
     Oracle Exadata/Exalogic
3.HA & HP
    CDN: akamai, bluecoat, chinacache, level3, 365media, kontiki, cdnetworks
     Monitoring: ntop, nagios, opsview, HP OVO, Gomez, mrtg, catci, orca, scom, munin, collected<nagios-collected, collectd-unixsock, collectd-python>
                      Tivoli<websphere monitoring>, opnet<app perf test>, loadimpact
     F5 LTM, Netscaler, varnish, squid, Cisco<CSS, ACE, GSS>
     Cluster: VCS, IBM HACMP, haproxy, LifeKeeper, hp ServiceGuard/TruCluster, DRBD<Distributed Replicated Block Device>
     Webscreen, netscreen, truecrypt, NDS DRM, McAfee, forefront<windows>
     Java: IBM MQ, Azul, Jetty, tomcat, websphere, glassfish, weblogic, hudson/jenkins CI
     quova #ip geolocation
     openldap, SUN iPlanet DS
     NetApp, EMC, HP, Oracle, Qlogic, Emulex, IBM, Dell, SGI, HDS, Brocade, Emulex, SUN ZFS
Categories: IT Architecture Tags: