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Informix Read-Only Access2021-02-17T10:14:22+00:00

Abstract

Informix DBAs are often asked to provide login details for a user account that should only be allowed to view data or run reports. In other database products such as Microsoft SQL Server, a suitable database level privilege is available, but this is not so easy with Informix Dynamic Server (IDS). This article describes how to achieve this, including a script to perform the bulk of the work.

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Informix Partition Defragmentation2021-02-17T10:12:46+00:00

Abstract

From Informix Dynamic Server (IDS) 11.70, syntax exists to merge extents for any table or index, even system catalog tables for which there was previously no solution. This article examines why it matters and provides methods to defragment any number of them in one run.

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Informix Upgrades and “oncheck”2021-02-16T16:04:59+00:00

Abstract

There is a standard recommendation to scan tables and indexes using the Informix “oncheck” tool for any integrity issues before an in-place database server upgrade that might otherwise make it fail. What is less well known is that it should be run afterwards in case problems have been caused by the upgrade. This article covers a specific scenario where this is necessary and how it can be more easily resolved.

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Informix Connection Logging2021-02-16T15:58:43+00:00

Abstract

There is no built-in way to view the history of connections to an IBM Informix Dynamic Server (IDS) database once they have terminated. Doing so can be the key to solving questions such as where a user is located or who has been performing particular SQL actions, whether it be for auditing, application improvement, or user training. This article outlines a simple solution that can be implemented to append connection details to an external text file as a permanent record, and goes further to describe how that can then be maintained and accessed with SQL.

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Informix 14.10 Manage Shared Memory Dumps2020-08-18T10:30:40+01:00

Abstract

Informix Dynamic Server (IDS) can be configured to save the contents of shared memory (as well as readable evidence in an “assert file” and stack trace) either when a critical error occurs or a trap is in place for specific error numbers. This can help IBM diagnose a problem by running “onstat” commands off-line to examine the state at time of error. However, if dumps happen repeatedly before the DBA can intervene, the file system nominated to store them may well fill. Saving a memory dump is also slow, intensive, and exclusive, so excessive repeats will further impede the instance, assuming it has stayed running, and if not will hinder any restart attempts until the dump has finished. Managed Shared memory dumps is the latest configuration parameter settings in IDS 14.10.FC4 that enable limiting the number and/or frequency of such dumps. These enhancements are described in the updated documentation pages for DUMPSHMEM and DUMPCNT in the IBM Knowledge Center, but are missing from What’s New in IDS 14.10 so may not be as well known.

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DIRECT_IO for Temporary Dbspaces2020-08-18T10:34:18+01:00

Abstract

Informix Dynamic Server (IDS) stores database objects in temporary “dbspaces” comprised of one or more “chunks” (physical storage devices). Historically, chunks were disk devices or logical volumes. In more recent years, with the advent of general-purpose network storage arrays and virtual machines, it became desirable to store chunks in file systems (“cooked files”). For applications needing comparable performance, this became a viable option with configuration parameter DIRECT_IO introduced in IDS 11.10, which enables files to be accessed using Kernel Asynchronous I/O (KAIO) with the O_DIRECT flag available in later operating system versions, bypassing file system buffering and caching. The manual page here states that “IBM Informix does not use direct I/O for cooked files used for Temporary DBSpaces chunks.” That is no longer accurate as of IDS 12.10.FC13 or 14.10.FC2 due to a feature still undocumented as at June 2020: see forum thread here. This article explores when/why/how this should be enabled.

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Common Table Expressions2020-08-13T14:28:25+01:00

Abstract

Common Table Expressions (CTE ) is an SQL feature is now common to all the major relational database products and was added to Informix Dynamic Server (IDS) in version 14.10. Replay and slides from a recent Webinar on this by IBM are here. This article describes the feature in a simpler way with complete real-world examples.

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Informix 14.10 Partial Indexes2020-08-18T12:32:43+01:00

Abstract

Best practice has always been not to create indexes on highly duplicate data. Scanning the entire table for a common value may be quicker, and updating an index can be very costly when many pointers to rows with the same value are spread over several pages. A work-around when an index is essential in this scenario is to extend the index with a more selective column, but this obviously makes it bigger. For the first time, a far better solution was provided in IDS 14.10.FC2. It’s known as Informix 14.10 Partial Indexes Partial Indexes (click for the relevant page in the IBM Knowledge Center). In this article, we will demonstrate how to identify where such indexes might be appropriate, how to create them, and how much smaller they can potentially be.

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Cloud Backups with Informix 14.102020-08-18T12:07:57+01:00

Abstract

For many, the choice of cloud backups versus another backup medium has always been a difficult decision. Backing up to tape is reliable, and tapes can easily be transported off-site, but rely on a lot of manual intervention.  Disk is fast and cheap these days, but the backups stay local to the server and at risk until moved elsewhere. Informix 14.10 has cloud backup support built in.  Using the Primary Storage Manager (PSM), cloud storage is presented as if it were just another local device.  This means backups can instantly be encrypted and stored off site with no additional scripts or other complications. Cloud backups are a secure way to store data off site. In this article we will demonstrate how to perform cloud backups with Informix 14.10 and effectively back up Informix archives to Amazon S3.  A working AWS account is required to do this.

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Informix 14.10 Integrated Backup Encryption2020-08-13T14:30:19+01:00

Abstract

We’ve discussed encrypting backups on Informix 11 and 12 using the BACKUP_FILTER and RESTORE_FILTER onconfig parameters in an earlier article.  While effective, this involved writing scripts, using external tools and managing encryption keys manually. Using the new onkstore utility (see technical article here), with Informix 14.10 Integrated Backup Encryption, ontape and onbar backups can now be encrypted and decrypted natively. As before, there is obviously some risk here, as if the keys are lost it can render your backups essentially useless.  We therefore strongly recommend only using this with a cloud based key store, as this method uses envelope encryption to ensure your backups can always be restored. Although we recommend using a cloud key store, for the purpose of this article, a local key will be used.  As above, we would not recommend doing so for a production system.  Read on to learn more about Informix 14.10 Integrated Backup Encryption:

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