Did anyone ever try \'transactionLogging\'

[fmulder]

The database of a WinCC OA project can get corrupted when you pull the power from the server. The help file mentions the config entry 'transactionLogging' as a possible solution. (see the text below). My questions:

* Did anyone try this. Will it work 100%
* What will it do for the performance of the DataManager

Here the text from the help-file:

Since the data is written only block by block into the RAIMA database an unsaved block can be lost at system crash and the stored data can be corrupted. The transaction logging, however, prevents a permanent damage of the database since an internal (data internal) transaction is only finished after all data is written to the disk. When the transactionLogging is activated (= 1), no database repair is necessary. If transaction logging is used, it takes priority over the values in the internal data manager DP. Activated transaction logging causes the data manager to operate slower as without transaction logging.

[buec]

Hi Frenk

We used transaction logging a few month on our development systems with WinCC OA 3.13 but the performance was realy bad especially for configuration changes like adding/deleting data points or configs. Also ASCII import takes a multiple of the time. So we decided not to use transaction logging in our projects.

Best regards
Christoph

[leoknipp]

Hello,

first of all - even if transaction logging is used there is no guarantee that the project can be started if the project was not stopped properly. When you pull the power cable for the server there is also no guarantee that the server can be started. In some cases some files outside of the WinCC OA database have been lost and then the project cannot be started also.

The risk to damage the database can be reduced when using transaction logging.

We did some tests for customers to find out the differences when using transaction logging. Also there have some improvements in WinCC OA (3.13 and 3.14) concerning the data manager when using transaction logging.

As Mr. Buecheler has mentioned adding/deleting datapoints takes a lot of time when transaction logging is activated. An activated transaction logging should not have a huge impact on other configuration tasks in the database.

You can use dynamic transaction logging (activated/deactivated using the dp-element _DataManager.TransactionLogging.Set). If you want create/delete datapoints transaction logging is turned off.

Best Regards
Leopold Knipp
Senior Support Specialist

[RudiKreiner]

We have transaction logging switched off for software development because ascii import is then much faster,
and switch it to on when we are done and deliver to software for better data base stability.

We found that doing large ascii imports with transaction logging on can actually block up the system, but adding the -commit option (see more information in help file9 will slow down the ascii import to avoid any negative side affects

[fmulder]

Rudi,

Does it mean that you use the transactionLogging in the 'field' ? What is your experience.

- Can you say something about performance (when not using Ascii manager)
- Any news about stability. Does it help ?

Thanks to all for their contribution. Most helpfull

Kind regards

Frenk

[RudiKreiner]

We have had transaction logging activated in all of our projects in the field for the last 5 years.
This may not be the only reason, but since then we have not had any problems with corrupt data bases any more.
Especially with the older 2.11 and 2.12 PVSS versions we often without transaction logging we often had corrupt data bases, though we suspect that the main cause was that the power was cut to our servers before shutting down PVSS which was caused by bad maintenance procedures or improperly configured UPS systems.

So from my point of view, I can only recommend activating it.

[fmulder]

Rudi

Thanks for your opinion. I will at least plan to test this functionality.
Good to hear that you have had no corrupted database 'in the field'.

I understand that the option is not a godo idea during engineering, but it does seems to make the 'field' situation more stable.

Thanks

Frenk