Aug 13 2020

Unable To Load Module Oracleasm in Oracle 12c

CRS (Cluster Ready Service) is not starting and getting ‘FATAL: Module oracleasm not found’ error on log files.

[root@ocmnode1 ~]# cat /var/log/messages

Aug 12 01:32:08 ocmnode1 modprobe: FATAL: Module oracleasm not found.
Aug 12 01:32:33 ocmnode1 modprobe: FATAL: Module oracleasm not found.
Aug 12 01:34:32 ocmnode1 modprobe: FATAL: Module oracleasm not found.

After checked in details found that oracleasm package / RPM was not working. 

[root@ocmnode1 ~]# oracleasm init
Creating /dev/oracleasm mount point: /dev/oracleasm
Loading module "oracleasm": failed
Unable to load module "oracleasm"
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Aug 09 2020

Migrating OCR, Voting Disk and MGMTDB to another ASM DiskGroup in 12c RAC

Sometime DBA need to move or migrate below mentioned files or DB to different ASM DiskGroup for difference reason. I will show how to move or migrate below mentioned files or DB from one ASM DiskGroup to Another:

  • How to move or migrate OCR and Voting Disk from one ASM Diskgroup to another.
  • How to move or migrate SPFILE and PWDFILE from one ASM Diskgroup to another.
  • How to move or migrate MGMTDB from one ASM Diskgroup to another.
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Aug 08 2020

Adding a Node to Oracle RAC 12c

Complete below list of tasks:

DBA may need to add a new node or existing node (which got deleted from cluster) into Clusterware.

List of tasks for New Node:

  • Install same version of OS
  • Setup environment variable
  • Install all required package including Oracleasm
  • Configure Networking (IP and others)
  • Check Time Synchronization 
  • Change Recommended Kernel Parameters for Oracle
  • Create Group and User (make sure these are same with existing Nodes)
  • Setup SSH configuration for grid user or (user which was used for GRID installation) between new node and other nodes.
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Aug 01 2020

Deleting a Node to Oracle RAC 12c

A node in the cluster may crash due to hardware or OS problems and is not recoverable. So DBA needs to delete a problematic node from clusterware. In this topic I will show discuss how to delete a node from two nodes RAC.

Two Nodes: ocmnode1 will be deleted

  • ocmnode1
  • ocmnode2

Deinstall Oracle Home:

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Jul 26 2020

Oracle Exadata Smart Flash Cache

Smart Flash Cache:

  • Oracle Exadata Smart Flash Cache stores frequently access data in Flash Storage which is very fast than other storage. This happens automatically and user don’t need to take any action to use this feature.
  • Flash Cache is Smart – it avoids caching data which will not be reused or which is too big to fit in cache.
  • The Exadata Storage Server Software also provides the Exadata Smart Flash Logging feature to speed database log I/O
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Jul 20 2020

Hybrid Columnar Compression

About Exadata Hybrid Columnar Compression

  • Oracle introduced basic compress feature from Oracle 9i version.
  • Exadata Hybrid Columnar Compression can be specified at Table or Table Partition and Tablespace Level.
  • Not Suitable for data which is frequently changing.
  • Locking at CU level instead of row level so potentially many rows could be locked instead of single row
  • Data needs to be loaded using direct path loads like Parallel DML, INSERT /*+ APPEND*/, direct path SQL Loader
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Jul 19 2020

Configure Distributed Command Line Interface (DCLI)

To manger and monitor Exadata Storage we can use two utility.

  • CELLCLI
  • DCLI

CELLCLI: Each Exadata Storage Cell is administered individually by using cellcli. But this utility can connect a local cell server. cellcli works with MS process to perform the administration task like creation of cell or grid disk.

DCLI: DCLI utility enables execution of commands on multiple database and storage servers.

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Jul 19 2020

Storage Indexes in Exadata System

What is Storage Index in Exadata System?

Storage Index in Exadata is another important feature which helps to reduce useless I/Os for query execution.

A storage index is a memory-based structure that reduces the amount of physical I/O performed in an Exadata cell. The storage index keeps track of minimum and maximum column values of a chunk in GRID Disk and this information us used to avoid useless I/Os.

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Jul 17 2020

Exadata Smart Scan

What is Smart Scan?

Smart Scan is one of the great feature in Oracle Exadata. With this technology storage send only required rows to database node from storage instead of entire Oracle Block. Multiple rows are stored in one Oracle Block but non-exadata system return entire block even only one rows is required. On the other hand, Exadata Storage returns only interested rows but not entire block.

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Jul 17 2020

Exadata Key Features

In this topic will be discussed with Exadata Key Features

  • Smart Scan or Cell Offloading
  • Storage Indexes
  • Hybrid Columnar Compression
  • IO Resource Manager
  • Smart Flash Cache
  • Flash Logging
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