What is Journaling?

Journaling is a critical IRIS feature and a part of what makes IRIS a reliable database. While journaling is fundamental to IRIS, there are nuances, so I wrote this article to summarize (more briefly than our documentation which has all the details) what you need to know. I realize the irony of saying the 27 minute read is brief.

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Working in support, I usually get asked how many days I should keep journals. Should it be two days or after two backups? More? Less? Why two?

The correct answer (for most of the environments) is that you should keep the journals since the last validated Backup. I.e., until you don't check if a Backup is valid (restoring the file and checking with the Integrity utility), you can't be sure there is a good copy of your data and can't purge the journals safely.

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Article
· Nov 24, 2023 4m read
Journal File Indexer

Hi community!

In this article, I'm excited to introduce my latest application, Journal File Indexer. The development of this application is rooted in the portal idea DPI-I-270.

In short, this application lets you load and index a log file in a database.

Why?

If you've ever used the log file search function in the management portal, you may have encountered a timeout error or even a blank page. This problem usually occurs when searching a large journal file. Journal File Indexer solves this problem by considerably increasing the speed of searches once the file has been loaded into the database.

Another problem arises during the restoration process. When searching for global entries in a log file to restore old or new values, the management portal doesn't have this specific functionality. A routine must therefore be coded to achieve this. Journal File Indexer comes to the rescue, incorporating a restore function!

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Recently I needed to restore a version of a production class, which was overwritten by compilation and running UpdateProduction. As the correct version was unavailable in the source control, I used journals to restore the data. Journals store a plethora of information about what's happening in the system and are quite a powerful tool. This article explains how to work with journals to extract the data you require.

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InterSystems FAQ rubric

If the system does not stop for 24 hours, old journal files will be deleted at 0:30 according to the "Journal file deletion settings".

A possible cause of journal files remaining that are older than the "Journal file deletion settings" is that there are transactions that remain open.

In that case, you will be able to delete the journal file by searching for processes executing transactions and finalizing the transactions.

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In this article I'd like to share with you a phenomena that is best you avoid - something you should be aware of when designing your data model (or building your Business Processes) in Caché or in Ensemble (or older HealthShare Health Connect Ensemble-based versions).

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InterSystems has corrected a defect that causes invalid database and journal records to be introduced when using a specific $LIST syntax. The likelihood of encountering this defect is very low but the operational impacts can be significant.

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Hi,

We have Mirroring established between NODE 1 & Node 2 . We have set the "cachesys" database enabled for Journalling. But we dont see the User Accounts , Roles, Resources created on Node 1 ( favoured Primary) reflected on Node 2 . Is creating them manually again is the only option for this ? . Is there any way to sync them or would adding %SYS to MIRROR a possible solution. Would it be great if anyone has faced this as we have an issue that during failovers Team is locked out .

Best Regards,

Arun Madhan

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Hi!

Currently, I'm working on a script using %SYS.Journal API.

My journal files are compressed, following the documentation the compression is zstd.

I tried to unzip a file with zstd tool, ex:

apt-get update
apt-get install zstd

zstd -d 20230806.001z -o 20230806.001

20230806.001z        : 92.03%   (909312 => 836859 bytes, 20230806.001) 

Unfortunately, the unzipped file is invalid:

Write ##class(%SYS.Journal.File).IsValidJournal("/usr/irissys/mgr/journal/20230806.001")

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In System Administration | Configuration | System Configuration | Journal Settings there is a check box for Freeze on error.

From reading the documentation, it sounds like the choice to freeze on error is one of system availability vs system integrity.

Curious to know whether Ensemble users choose to freeze on error or not.

If you have a best practice recommendation based upon your experience or knowledge, that would be helpful information too.

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Question
· Apr 23, 2021
Log (Journal) shipping

I am new to Cache, we are trying to move a 4 TB database over the internet, but this will be take too long to copy the single backup file. In Oracle and MS-SQL Server there is an option of doing log shipping. Is there such an option in Cache?

I want to copy the initial backup file one weekend, then keep sending the Journals (logs) the new location.

Thank you,

Eudoro

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I am attempting to failover my TEST environment to the Backup, and I keep getting an error stating that

06/01/25-18:47:54:516 (11864) 1 [Utility.Event] Primary startup failed, failed to read header of /archive/journal/MIRROR-IRISTEST-20250513.007 (file #63653)

however, when I go to /archive/journal/, I am not finding any record of MIRROR-IRISTEST-20250513.007 (file #63653)

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Hello, community!

I've stumbled on some unexpected behavior, and decided to check with you if this is normal. Basically, I'm rebuilding indices and the result is not journaling (which leads to missing indices at shadow server).

The $ZV is "Cache for UNIX (Red Hat Enterprise Linux for x86-64) 2015.2.1 (Build 705U) Mon Aug 31 2015 16:53:38 EDT"

I have an example class

Class tmp.A As %Persistent;

Index IP1 On P1;

Property P1 As %String;

for example there is one object which have P1 = 1, so

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Question
· Oct 7, 2022
Mirror Failover Settings

Hi All,

Our mirrored HealthShare environment has failed over a few times recently due to underlying infrastructure issues (that are being worked on and resolved).

In the HealthShare logs we are seeing:

10/06/22-00:54:35:925 (4736) 1 Journal Daemon has been inactive with I/O pending for 10 seconds:
gjrnoff=524741316,iocomplete=523852600,filecnt=1011,fail=0
10/06/22-00:54:55:086 (4736) 3 CP: Pausing users because Journal Daemon has not shown
signs of activity for 30 seconds. Users will resume if Journal Daemon is active again

My question is:

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In the Windows Ressource Manager I can observe multiple parallel processes coming from cache.exe with read operations to journaling files.

All except one of these processes have the same reads(Byte/s). The processes point to different journal files and constantly read between 200 and 3000 Bytes/s.

The corresponding process via PID in the management portal of Caché shows the process %SYS.Monitor.Control.1. In 3 days of uptime on the server it has run 181.632.583 commands and modified 32.140.642 globals.

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Just wondering if anyone knows if there is a way to get daily emails or alerts about changes to a cache database. I know that all of that information is contained within the journal files, just wondering if there is a way to bundle it up each day and send it off for auditing, etc.

Any solution where a plain-text/readable format of changes to the cache database could be sent or stored for review would solve the issue.

Thanks!

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