As we all well know, InterSystems IRIS has an extensive range of tools for improving the scalability of application systems. In particular, much has been done to facilitate the parallel processing of data, including the use of parallelism in SQL query processing and the most attention-grabbing feature of IRIS: sharding. However, many mature developments that started back in Caché and have been carried over into IRIS actively use the multi-model features of this DBMS, which are understood as allowing the coexistence of different data models within a single database. For example, the HIS qMS database contains both semantic relational (electronic medical records) as well as traditional relational (interaction with PACS) and hierarchical data models (laboratory data and integration with other systems). Most of the listed models are implemented using SP.ARM's qWORD tool (a mini-DBMS that is based on direct access to globals). Therefore, unfortunately, it is not possible to use the new capabilities of parallel query processing for scaling, since these queries do not use IRIS SQL access.

Meanwhile, as the size of the database grows, most of the problems inherent to large relational databases become right for non-relational ones. So, this is a major reason why we are interested in parallel data processing as one of the tools that can be used for scaling.

In this article, I would like to discuss those aspects of parallel data processing that I have been dealing with over the years when solving tasks that are rarely mentioned in discussions of Big Data. I am going to be focusing on the technological transformation of databases, or, rather, technologies for transforming databases.

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Introduction

Despite the fact that InterSystems has long recommended using external backup tools, many users have opted to use the internal Online Backup facility, which is included in all distributions of InterSystems products (IRIS Data Platform, Caché, etc.). The reasons why are quite obvious:

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In old Caché versions it was possible to create a new role based on predefined %Developer by copying it and adding some resources as needed. It was true at least from 2010.1 to 2015.1.

After upgrade from 2015.1.4 to 2017.2.1 it turned that it's only partially true now. User with a "New-Developer" role can enter Studio and open existing cls/mac/etc for editing and everything is OK unless he tries to create something new (Ctrl-N), than he gets a pop-up with %msg: <User xxx does not have enough privilege to execute stored procedure %CSP.StudioTemplateMgr_Templates>

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Article
Alexey Maslov · Nov 23, 2017 12m read
Where is my global stored?

It's well-known that namespace global mapping helps us to write code independent on database storage details (Caché instance name, directory path). But sometimes we can face problems accessing an unsubscripted global which has subscript level mapping (SLM) defined. Most of such cases are evident and associated with administrative tasks that should be done on database level, but some of them can confuse even an experienced developer. Just to start:

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If you have an app that uses some Caché client Windows components that are not included into CacheODBC distribution (e.g. CacheActiveX.dll), you need to proceed Caché client installation on end user's client computers and/or MS Terminal Servers. Being a part of Caché client's installation, Caché Cube is installed along with other components and is autostarted with every user's session. So, it becomes visible to every user.

To make it completely invisible, you can just move CACHE.lnk file from

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Article
Alexey Maslov · Nov 17, 2016 11m read
ECP and Process Management API

The technology of load balancing between several servers with relatively low capacity has been a standard feature of Caché for quite a while. It is based on the distributed cache technology called ECP (Enterprise Cache Protocol). ECP provides a host of possibilities for horizontal scaling of an application, and yet keeping the project budget fairly low. Another apparent advantage of ECP network is the possibility to conceal its architecture in the depths of Caché configuration so that applications developed for the traditional (vertical) architecture can be fairly easily migrated to a horizontal ECP environment. The ease of this process is so mesmerizing, that you start wishing it was always this way. For instance, everybody is used to having a possibility to control Caché processes: the $Job system variable and associated classes/functions work magic in skilful hands. Stop, but now processes can end up being on different Caché servers…

This article is about how to gain as much transparency in controlling processes in ECP environment as in traditional (non ECP) one.

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The goal of this writing was to illustrate how to restore backup before the patch would be applied. The alert notes that: 

The risk can be avoided by applying journals from the beginning of the journal file that was switched to at the start of the backup, rather than accepting the default of starting from the journal marker position.

Having non-patched Caché 2015.1.4, I ran sample database backup and restore just to get where I should answer "No". Collecting journal info from the backup log: 

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After reading Stephen Wilson's article "Windows 7 performs shutdown too fast for Cache to close and so it gets forced down" I've recalled another solution that was based on Local Group Policy, which allows to control extra actions that should occur on computer startup or shutdown. How to add a computer shutdown script is well documented in MS Technet article.

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