$LIST string format and %DynamicArray and %DynamicObject classes

IRIS, and previously Cache, contain several different ways to create a sequence containing a mixture of data values.  A data sequence that has been available for many years is the $LIST string.  Another more recent data sequence is the %DynamicArray class, which along with the %DynamicObject class, is part of the IRIS support for JSON string representation.  These two sequences involve very different tradeoffs.

$LIST String Format

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The DeclarativeCOS project is a heartfelt cry about programming in the COS language.

The purpose of the project is to draw attention of the public to improving the inner core of COS.

The idea of the project is the support of a laconic syntax for cycles and collections.

So what is this laconic something that I have come up with? Welcome to the examples below!

Examples

The key concept underlying the project is the declarative approach to writing code. You need to specify WHAT should be used and HOW.

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Note (June 2019): A lot has changed, for the latest details go here

Note (Sept 2018): There have been big changes since this post first appeared, I suggest using the Docker Container version, the project and details for running as a container are still in the same place  published on GitHub so you can download, run - and modify if you need to.

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Article
John Murray · Apr 24, 2017 1m read
Diagnosing the cause of <PROTECT> errors

If your application is raising <PROTECT> errors and you're finding it hard to work out why, here's a way to get additional information.

First, if auditing is not already enabled, turn it on:

Then use "Configure System Events" (highlighted above) and locate the event named %System/%Security/Protect. In the screenshot below I used the Filter field to do this (type "protect" - highlighted below - and press TAB):

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InterSystems states that Caché supports at least three data models – relational, object and hierarchical (globals). On can work with data presented in relational model in a program written on C# the same way one works with any other relational DB. To work with data presented by object model in C# one needs to use .NET Managed Provider or some kind or ORM. And starting with version 2012.2 one can work directly with globals (or use direct access to hierarchical data) via Caché eXTreme for .NET

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This text is a continuation of my article where I explained the structure a Caché database. In this article, I described the types of blocks, connections between them and their relation to globals. The article was purely theoretical. I made a project that helps visualize the block tree - and this article will explain how it works in great detail.

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It has been noticed that some customers running JAVA programs (for example, FOP) on AIX would see the server eventually running low then out of memory. Customer would notice the system pages heavily and user experience becomes bad. And the server would crash when out of memory.

 

When the problem happens, we can see in ipcs a lot of shared memory segment marked for deletion (Capital D at the beginning of MODE section). This means they will not disappear until the last process attached to the segment detaches it.

 

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C:\data\backup.bat :

C:\InterSystems\Ensemble\bin\cache -s"C:\InterSystems\Ensemble\Mgr" -U%%SYS ##Class(Backup.General).ExternalFreeze() <C:\data\login.scr 

echo %ERRORLEVEL%

rem note that we need to check errorlevel from highest to lowest here....

if errorlevel 5 goto OK

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If you want to dynamically serve images as a property of JSON then there is no perfect encoding solution. One method used frequently is to Base64 encode the image. Whilst there are some negatives to doing this, such as data inflation, there are some positives to working with Base64 images inside the browser.

Let's say you have an image placeholder on a web page...

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It is with great pleasure that the CIUSSS de l'Estrie - CHUS is sharing the mocking framework it developed and presented at the InterSystems Summit 2017.  I will update this post with more detailed instructions in the next few weeks but I wanted to share the code and presentation quickly : 

https://gitlab.com/ciussse-drit-srd-public/Mocking-Framework

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Those of you who keep an eye on developments in the mainstream of IT will be aware that a major upheaval has been occurring over the last 5 or so years, in which JavaScript has exploded in popularity and importance.  Largely as a result of its server-side incarnation - Node.js - it has broken free of just being the scripting language that you use in web browser, to becoming the world's most popular language and enterprise technology of choice.

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Article
Robert Cemper · Aug 17, 2017 2m read
Repairing your Index

If you have to fill or change your class data other than by standard object filer or SQL filer
you also have to get your indexes in line with your data.
Rebuild Index might be time consuming exercise eventually blocking access at all.

I just detected ##class(%Library.Storage).%ValidateIndices()

Not really new, but in 2015.1.1 ,  2016.2.1 there was not a single character of documentation to it.
Now I see on latest

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Article
Peter Everett · Sep 22, 2016 3m read
Windows write caching

(This article was reviewed in February 2021.  It is still relevant to Caché-based installations and similarly applies to IRIS-based installations.)

This article discusses the Windows write caching setting which can leave systems vulnerable to data loss or corruption in the event of power loss or operating system crash.  The setting is on by default in some Windows configurations.

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InterSystems Data Platform includes utilities and tools for system monitoring and alerting, however System Administrators new to solutions built on the InterSystems Data Platform (a.k.a Caché) need to know where to start and what to configure.

This guide shows the path to a minimum monitoring and alerting solution using references from online documentation and developer community posts to show you how to enable and configure the following;

  1. Caché Monitor: Scans the console log and sends emails alerts.

  2. System Monitor: Monitors system status and resources, generating notifications (alerts and warnings) based on fixed parameters and also tracks overall system health.

  3. Health Monitor: Samples key system and user-defined metrics and compares them to user-configurable parameters and established normal values, generating notifications when samples exceed applicable or learned thresholds.

  4. History Monitor: Maintains a historical database of performance and system usage metrics.

  5. pButtons: Operating system and Caché metrics collection scheduled daily.

Remember this guide is a minimum configuration, the included tools are flexible and extensible so more functionality is available when needed. This guide skips through the documentation to get you up and going. You will need to dive deeper into the documentation to get the most out of the monitoring tools, in the meantime, think of this as a set of cheat sheets to get up and running.

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Article
Brendan Batchelder · Sep 20, 2016 4m read
Diagnosing Framing Errors

Framing refers to the characters that mark the start and end of an HL7 message (or other types of framed messages).  Most HL7 services and operations have a Framing setting that allows the user to define this framing.  The most common choices are available as defaults, but with the AsciiMM/NN setting, components can be configured to recognize any framing characters.

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The Art of Mapping Globals to Classes (4 of 3)

The forth in the trilogy, anyone a Hitchhikers Guide to the Galaxy fan?

If you are looking to breathe new life into an old MUMPS application follow these steps to map your globals to classes and expose all that beautiful data to Objects and SQL.

If the above does not sound familiar to you please start at the beginning with the following:

The Art of Mapping Globals to Classes (1 of 3)

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