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Why Bitmap Indexes Can Wreck OLTP Systems

Bitmap indexes might seem like a great idea—they save space and are fast for certain types of queries. But in high-traffic OLTP systems, they can be a nightmare. Why? Because they don’t play well with frequent updates and lots of users at the same time. In fact, they can cause serious blocking and performance problems.Continue reading “Why Bitmap Indexes Can Wreck OLTP Systems”

AI for DBAs: Understanding AI Vectors

Imagine you’re building a robot librarian. Instead of organizing books by titles or authors, it groups them by meaning—romance novels near poetry, tech manuals near science fiction. This is exactly what AI vector databases do: they turn messy data (words, images, sounds) into meaningful numbers that machines can understand. Let’s break it down. 1. AI Vectors: Turning Chaos IntoContinue reading “AI for DBAs: Understanding AI Vectors”

How to fix “DROPPED” griddisk in Cell

You may encounter a situation where a grid disk is in a dropped status in oracle exadata cell storage. This issue can be identified using the following command: Additionally, the ASM alert log may show errors like: This error indicates that the grid disks do not have the same size, which is causing issues inContinue reading “How to fix “DROPPED” griddisk in Cell”

Unlocking Performance with Oracle 23AI’s True Cache

Oracle 23AI introduces a groundbreaking feature called True Cache, which provides an in-memory caching layer for frequently accessed data. This significantly improves read performance, especially in environments where quick access to repetitive data queries is critical. However, don’t confuse it with the “In-Memory” feature, as both serve very different use cases. Let’s explore the details.Continue reading “Unlocking Performance with Oracle 23AI’s True Cache”

Benefits of Zstandard Compression in Oracle 23ai HCC

In Oracle Database 23ai, significant improvements have been made to Hybrid Columnar Compression (HCC), with the default compression method now utilizing Zstandard (Zstd) instead of the previous algorithms, zlib and bzip2. But what exactly is Zstandard, and how does it differ from zlib and bzip2? Zstandard is a lossless data compression algorithm developed by YannContinue reading “Benefits of Zstandard Compression in Oracle 23ai HCC”

How to patch Exadata PDU

Recently, I collaborated with a colleague to promote our Exadata system to a new Oracle Enterprise Manager (OEM) server. However, we encountered issues when attempting to promote the Power Distribution Unit (PDU). After consulting My Oracle Support (MOS), we decided to address potential bugs by applying the latest PDU patch before proceeding with the promotionContinue reading “How to patch Exadata PDU”

What should we do if the Flash Cache is degraded in an Exadata cell

Flash cache plays a critical role in Exadata performance. When issues arise, it’s crucial to understand the symptoms and resolution steps. Typically, each flash cache comprises four flash disks. If one flash disk fails, the cell service automatically removes it while continuing to operate with the remaining three disks. In most cases, immediate intervention isContinue reading “What should we do if the Flash Cache is degraded in an Exadata cell”

ZDLRA ERROR: Filesystem label ESP is found more than once.

Recently, while patching a ZDLRA X7-2 full stack to version 21.1.202405, I encountered an error during the dbnode precheck. This blog post details the issue and its resolution. The Error During the precheck, the following error was encountered: 2024-09-17 15:13:11 +0200 :ERROR : dbnodeupdate.sh precheck failed on one or more nodes SUMMARY OF WARNINGS ANDContinue reading “ZDLRA ERROR: Filesystem label ESP is found more than once.”

Exadata, How to unlock ilom’s root account

After upgrading to ILOM 5.x, password locking is enabled. So root account could be locked after you change password, especially you forgot change it in oem. You can find more detail in Doc ID 2670512.1 . If the root account is locked, you must unlock and changing password cannot unlock the account. As you cannotContinue reading “Exadata, How to unlock ilom’s root account”

How to create new VM in Exadata

In my exadata environnment, it has 2 compute nodes, 3 cells, 3 VM clusters.Let’s see how to add new VMs cluster .First, add new IPs in DNS server. In my case: exavm01clu04: 172.22.1.241 exavm02clu04: 172.22.1.242 exavm01clu04-vip:172.22.1.244 exavm02clu04-vip:172.22.1.243 scan: 172.22.1.245 172.22.1.246 172.22.1.247 Second, downloading new OEDA(Patch 30640393) , start oeda server and create new VM configContinue reading “How to create new VM in Exadata”