Article
· 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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Imagine that your .NET project uses the Caché DBMS and you need a fully-functional and reliable authorization system. Writing such a system from scratch would not make much sense, and you will clearly want to use something that already exists in .NET, e.g. ASP.NET Identity. By default, however, this framework supports only its native DBMS – MS SQL. Our task was to create an adaptor that would let us quickly and easily port Identity to the InterSystems Caché DBMS. This work resulted in creation of the ASP.NET Identity Caché Provider.

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Article
· Sep 21, 2016 7m read
REST in Pieces

A beginners guide to develop Ensemble RESTful web services.

Background

Before you start reading this short introduction please go through the on-line documentation of Ensemble with special attention to chapter “Creating REST services and clients with Ensemble”.

The approach in the documentation is undisputable the fastest and easiest way to create RESTful services. As a beginner I went through the documentation and I had several questions. This short article is listing those questions plus my humble answers.

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Article
· 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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NewBie's Corner Session 27 Traversing A Global with $Order Part 1

Welcome to NewBie's Corner, a weekly or biweekly post covering basic Caché Material.

Traversing A Global

Perhaps the most difficult concept in Caché/MUMPS is its Global Structure. This session and several that follow it deals with the Global Structure. However, just presenting the material will not guarantee your understanding of it. You must experiment with the data and concepts that are presented.

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Article
· Sep 14, 2016 4m read
Creating a Dummy SOAP Web Service

A “Dummy” SOAP Web Service

When dealing with SOAP in Caché, it is sometimes necessary to debug errors by directly accessing (and sometimes editing) the XML which is sent, i.e. the SOAP request and subsequent SOAP response. If you’re debugging a Caché web service, it is often useful to use a tool such as SoapUI (https://www.soapui.org/) to manually create and control the SOAP request, so that the effect of adjustments can easily be seen on the Caché web service.

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NewBie's Corner Session 26 Globals and Arrays Part 2

Welcome to NewBie's Corner, a weekly or biweekly post covering basic Caché Material.

Globals, Arrays, and Variables Part 2

A thorough understanding of Globals, Arrays, and Variables is foundational for every Caché developer.

Uniqueness of the Caché Global Structure or database

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Have some free text fields in your application that you wish you could search efficiently? Tried using some methods before but found out that they just cannot match the performance needs of your customers? Do I have one weird trick that will solve all your problems? Don’t you already know!? All I do is bring great solutions to your performance pitfalls!

As usual, if you want the TL;DR (too long; didn’t read) version, skip to the end. Just know you are hurting my feelings.

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This short article was motivated by a problem of one of my customers. They use Ensemble to integrate many systems, some of them use just plain files.

So they naturally selected File Outbound Adapter to write into target file. Things were running smoothly for years, until recently, when the volume of data being written to the file reached large size of tens of megabytes. The operation took around half an hour to complete, causing timing problems where subsequent operations within the process had to wait, and third party system was not happy to wait so long.

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NewBie's Corner Session 25 Globals, Variables, and Arrays Part 1

Welcome to NewBie's Corner, a weekly or biweekly post covering basic Caché Material.

Globals, Arrays, and Variables

A thorough understanding of Globals, Arrays, and Variables is foundational for every Caché developer.

A Global may be:

Scalar (a single element), as in a Global Variable

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Mirror Outage Procedures

Caché mirroring is a reliable, inexpensive and easy to implement high availability and disaster recovery solution for Caché and Ensemble-based applications. This article provides an overview of recommended procedures for dealing with a variety of planned and unplanned mirror outage scenarios.

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Article
· Sep 7, 2016 5m read
Running HealthShare XSLTs from Terminal

HealthShare uses a lot of XSLTs. These are used to convert IHE medical documents to SDA (internal HealthShare format) and back to IHE formats, to create summary reports, and to deal with IHE profiles (e.g., patient information query, document provide and register). Customers may customize the XSLTs to customize reports or for other reasons.

For debugging and development, it is very convenient to be able to run an XSLT from Terminal.

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Let's say we have two serial classes, one as a property of another:

Class test.Serial Extends %SerialObject
{
Property Serial2 As test.Serial2;
}

Class test.Serial2 Extends %SerialObject
{
Property Property As %String;
}

And a persistent class, that has a property of test.Serial type:

Class test.Persistent Extends %Persistent
{

Property Datatype As %String;

Property Serial As test.Serial;

}

So it's a serial, inside a serial, inside a persistent object.

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Mirroring 101

Caché mirroring is a reliable, inexpensive, and easy to implement high availability and disaster recovery solution for Caché and Ensemble-based applications. Mirroring provides automatic failover under a broad range of planned and unplanned outage scenarios, with application recovery time typically limited to seconds. Logical data replication eliminates storage as a single point of failure and a source of data corruption. Upgrades can be executed with little or no downtime.

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Article
· Sep 2, 2016 2m read
Advanced URL mapping for REST

By now it's a commonplace how to implement a basic REST API in Caché and there is good documentation about it here: REST in Caché

A question that comes up from time to time is:

How can I make a parameter in my REST url optional?

Simply put, is it possible to create a URL map in Caché that maps a URL like this:

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I was recently troubleshooting a problem on a Linux (RHEL) instance of 2016.1 at a site. For policy reasons their sysadmins wanted to update the Caché installation so it used network accounts for its cacheusr and iscagent users and groups instead of the locally-created ones that had been set up during original install of Caché.

To do this they ran various commands including chown

Afterwards non-root users couldn't obtain a terminal session using the csession command. Instead they receive this message:

cache: Permission denied

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NewBie's Corner Session 20 Parameters and Status Part I

Welcome to NewBie's Corner, a weekly or biweekly post covering basic Caché Material.

Parameters

Parameters are another name for Variables when used in passing data from one Routine to another.

Let us say we have 2 routines (RtnA and RtnB), and we want to pass 3 parameters (Parm1, Parm2, Parm3) from RtnA to RtnB.

RtnA would look like:

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Article
· Aug 31, 2016 1m read
DeepSee cubes building troubleshooting

Hi!

Sometimes you see that call to DeepSee cube building method:

w ##class(%DeepSee.Utils).%BuildCube("CubeName")

does nothing.

Here are my 2 cents on possible reasons.

1. Run DeepSee Reset method in certain Namespace:

NAMESPACE> w ##class(%DeepSee.Utils).%Reset()

and try again.

2. Make sure, that all the indices in your base class for the cube are rebuilt, rebuild them and run it again:

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Welcome to NewBie's Corner, a weekly or biweekly post covering basic Caché Material.

MUMPS verses Caché, what's the difference?

MUMPS was developed at Massachusetts General Hospital during the 1960s. Through a series of experiences and companies over the years eventually MUMPS evolved into Caché. Some deny this but the facts are there. You can read through the various websites with Wikipedia and make up your own mind. The closest way to explain this is that Caché is a superset of MUMPS.

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