Identification of under-performing disks in Exadata

Database Management and Performance
| May 19, 2013

Starting with Exadata software version 11.2.3.2, an under-performing disk can be detected and removed from an active configuration. This feature applies to both hard disks and flash disks.

About storage cell software processes

The Cell Server (CELLSRV) is the main component of Exadata software, which services I/O (more...)

Where is my data

Database Management and Performance
| Oct 27, 2012
Sometimes we want to know where exactly is a particular database block - on which ASM disk, in which allocation unit on that disk and in which block of that allocation unit. In this post I will show how to work that out.

Database instance

In the first part of this exercise I am logged into database instance. Let's create a tablespace first.

SQL> create tablespace T1 datafile '+DATA';
Tablespace created.

SQL> select f.FILE#, f.NAME "File name", t.NAME "Tablespace name"
from V$DATAFILE f, V$TABLESPACE t
where t.NAME='T1' and f.TS# = t.TS#;

     FILE# File (more...)

When will my rebalance complete

Database Management and Performance
| Jul 22, 2012

This has to be one of the top ASM questions people ask me. But if you expect me to respond with a number of minutes, you will be disappointed. After all, ASM has given you an estimate, and you still want to know when exactly is that rebalance going to finish. Instead, I will show you how to check if the rebalance is actually progressing, what phase it is in, and if there is a reason for concern.

Understanding the rebalance

As explained in the rebalancing act, the rebalance operation has three phases - planning, extents relocation and compacting. (more...)

Exadata motherboard replacement

Database Management and Performance
| Jun 22, 2012

This photo story is about a motherboard replacement in an Exadata X2-2 database server (Sun Fire X4170 M2).

While setting up a half rack Exadata system, we discovered a problem with the motherboard in database server 4, so we got ourselves a new one. Even for an internal system, I had to log an SR, get our hardware team to review the diagnostics and have them confirm that a new motherboard is required. I had a full customer experience with me being both the customer and Support Engineer! Anyway, a replacement motherboard arrived the next day.














We stopped the clusterware (more...)

ASM in Exadata

Database Management and Performance
| Apr 1, 2012

ASM is a critical component of the Exadata software stack. It is also a bit different - compared to non-Exadata environments. It still manages your disk groups, but builds those with grid disks. It still takes care of disk errors, but also handles predictive disk failures. It doesn't like external redundancy and ACFS, but it makes the disk group smart scan capable. Let's have a closer look.

Grid disks

In Exadata the ASM disks live on storage cells and are presented to compute nodes (where ASM instances run) via Oracle proprietary iDB protocol. Each storage cell has 12 hard disks (more...)