PLC Warm, Cold Back Up

Hi,

Can Anyone tell me that, what is Warm(Hot) and Cold Back up in PLC

If I can use the analogy of a car

If I made the car back up by pushing the car backwards out of the garage is the engine hot or cold.

If I started the motor to make the car back up out of the garage is the engine hot or cold.

If this does not answer your question then could it be that we are lacking alot of details.

I've heard of cold, warm and hot restart, but never of cold and warm backup. What brand and type of PLC are you talking about?

Regards,

In general terms, hot backup usually means on the fly and takes little to no intervention with a seamless transistion and no loss of productivity. A cold backup would mean loss of productivity as an offline dump of a backup is performed.

never heard that homework question before. Kudos to your prof... That's a new one!

Since you registered in 2005, I am guessing that this is not homework.

Without being certain, my guess would be that a cold backup does not have variables, and the hot backup does.

I would say that a cold backup has the machine down, while the hot backup is when it is running. The only difference would be the state of the variables.

1. What is cold backup, hot backup, warm backup recovery? - Cold backup (All these files must be backed up at the same time, before the databaseis restarted). Hot backup (official name is ‘online backup’) is a backup taken of each tablespace while the database is running and is being accessed by the users.

Its amazing what wikipedia will turn up. this is an excerpt from a Java site.

QUESTION: What are the differences between “hot”, “warm”, and “cold” server backups?
ANSWER: Definitions of these terms vary a bit across the industry, generally:

• Cold server backups refer to those machines which have software installed and configured, but then are turned off.
• Warm backups are those which are turned on periodically to receive backups of data from the production servers. For example, warm backups are used in mirroring, replication, and log-shipping scenarios.
• Hot backups are those which are frequently turned on and ready to move into production mode immediately. These are typical in failovers within a cluster.

this is the definitions in regards to microsoft

In the old S5 world, there was a COLD BOOT and a WARM BOOT. Cold was from a power OFF to power ON condition, WARM is from Program to Run

In the PC industry warm boot is restart, cold boot is from PC off to on to program that in assembly was simply controlled by the value in the DH register. if the value was 1234 its a cold boot if its anything but its warm boot

There are several variants to 'hot' backup.
1) Hot Standby - 2 CPU's, 2 power supplies, changeover unit, common I/O. This variant is seamless - both CPUs scan the program all the time. If the CPU in charge fails, the other takes over seamlessly. The only thing the user will notice is an alarm on the failed CPU. The power supply chageover is also seamless - I suspect theyt just run the 2 power supplies together through a set of diodes. I do this all the time with batteries on generator systems - use bridge rectifiers.
2) Hot Standby with dual I/O systems. This variant is a complete redundant system. If something fails on one PLC the other takes over. Very expensive and can quite often introduce hundreds/thousands of new single points of failure as many inputs quite often have to be duplicated by using 2 pole relays.
These types of systems also normally allow the replacement of faulty I/O cards on the fly without turning off the PLC processor or power supply - pretty dangerous - there would have to be an awfull lot of planning to allow that to take place.
Warm standby is a bit of a moot point - Schneider alledgedly have a warm standby system but I have not investigated it all all. A method I have seen used that could be described as warm, or possibly even almost hot, standby utilises 2 PLCs running in parallel. A bit is held on permanenly (always on bit) driving a relay. The relay feeds into the second PLC. While ever the relay is on the (output off) bit is held on in the second PLC. If the relay from the first PLC turns off the second PLC takes over virtually instantly - there is a very minor delay for the send PLC 'outputs off' bit to reset and a slight physical delay while the outputs and output relays/contactors etc turn on.
Cold standby - never heard of it - physically replace the PLC?

I find the hot backup defination from Rockwell's Industrial Automation Glossary
(http://literature.rockwellautomation.com/idc/groups/literature/documents/qr/ag-qr071_-en-p.pdf)

Hot Backup
A programmable controller system configuration consisting of a primary
and a backup (secondary) processor. If the primary processor fails, the
backup processor takes over operations automatically.

However cannot find Cold Backup in it.
I guest maybe it would mean a programmable controller system configuration consisting of a primary
and a backup (secondary) processor. If the primary processor fails, the
backup processor takes over operations "manually". Which is unpractical in the sense on automation industries.