Global journaling records all global update operations performed on a database, and used in conjunction with backup makes it possible to restore a database to its state immediately before a failure or crash.
While backup is the cornerstone of physical recovery, it is not the complete answer. Restoring a database from backup does not recover global updates made since that backup, which may have been created a number of hours before the point at which physical integrity was lost. These post-backup updates can be restored to the database from journal files after the database is restored from backup, bringing the database up to date. Any transactions open at the time of the failure are rolled back to ensure transaction integrity.
I'm working for an organisation that is running a very old version of InterSystems Cache (5.016) which runs on AIX . The last two times we have re-booted Cache, we have encountered rollbacks. I've been asked two questions. During the rollback it was "How long is it going to take?" and after the system returned, it was "So what caused it?". My answer to both was "I don't know".
InterSystems has been at the forefront of database technology since its inception, pioneering innovations that consistently outperform competitors like Oracle, IBM, and Microsoft.
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!
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.
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
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.
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.
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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