Dmitry Maslennikov · Jun 1

Mirroring Ensemble service information

I have some system with heavy production. There are about 500GB of journals daily. And I'm looking at the ways, how to decrease the amount of data that appeared there.

I found no way, on how to split have the journal separately for mirroring databases and for others. So, I'm thinking about moving some of the globals to CACHETEMP. So, they will disappear from journals. So, thinking about Ens.* globals, I have about 30% of data in journals just for such data. Which production data can be safely moved to CACHETEMP, with no issues for mirroring?

Or, maybe you have some other suggestions, how to focus journaling more on important data.

Product version: Caché 2017.1
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Alternatively, you can create your own separate database that you are able to manage yourself and mark the setting of Journal to 'No'. Then map all not so important globals to that DB.

You should know that even in such a database with switched-off journalling, data will still appear in journals if data changed in transactions.

My question was, just exactly about that data stored for Ensemble, should I keep it in a mirror, or, may omit it?

There are few considerations here:

1. If you are using a failover (sync) mirror, you will need to that Ens.* data on the backup so a switch can be done seamlessly, and Ensemble production can start from the exact same point when failure occurred.

2. mapping any globals into a non-journal database will still have them on the journal when the process is "in transaction". Ensemble production is writing everything "in-transaction"

3. Mapping Ens.* to another DB is good idea if you have several disks, and you want to improve I/O on your system (specifically within cloud VMs that usually have a bit slower disks than on-premise). Another option is to let the system purge Ensemble data regularly and maybe keep less days of history.

4. Mirror journals are regularly being purged after all sync/a-sync mirror members got them.

I think the WRC would be the only ones who could tell you what could be moved into CACHETEMP unless you found someone else  who they had told already.

If you just don't want to store so many journals you could just backup multiple times a day and do a journal purge.

Congratulations on using Ensemble to the point you have this problem.