[Info-vax] RMS journaling - how it works (for dummies)

[Hein RMS van den Heuvel]

On Sunday, July 16, 2023 at 6:51:52 AM UTC-4, d45 n0x8!7 wrote:
> Hello Old$Boys! 
> 
> Can u help me to search a reference to info about of RMS journaling? May be DEC Journal or something other ?

For full understanding you should start with the documentation as per Jen-Erik's link.
It may be useful to point out that RMS Journaling is based on physical 'buckets', not logical records in the files.
The implication of that is that there is potentially much more data being journaled than there is data changed.
It's goal is to present a consistent file for a given point in time.
AI journaling to re-apply changing up to a selectable time starting from a backup.
BI journaling to 'undo' changes back to a selectable time starting from a live file
RU journaling to create transactional semantics across files allowing a single commit (or rollback) for multiple record changes.

Did you just want an explanation (how deep?) or do you have a business requirement for which you think RMS-Journaling might offer a solution? What is the exact problem you are trying to solve (if any).

A relatively common Journaling desire is Change Data Capture (CDC) which RMS Journaling does NOT offer.
The desire there being to have access to individual changed to records, either for auditing purposes (who changed what when) or to be able to forward such changes to another system or to a database.

There is a Commercial product called RMS-CDC owned by Brian Schenkenberger which can do full CDC for any and all file changes  including before-images based on a magic RMS intercept.

VSI has a prototype CDC based on the standard SSI (System Service Intercept) which required the programs to cooperate and declare they want they actions to be intercepted. It has good potential but does not offer Before Images (which may or might not be critical).

Hope this helps,
Hein.