How Flash Cache Compression Works in Exadata?

Flash cache compression dynamically increases the logical capacity of the flash cache by transparently compressing user data as it is loaded into the flash cache. 

This allows much more data to be kept in flash, and decreases the need to access data on disk drives. 
The I/Os to data in flash are orders of magnitude faster than the I/Os to data on disk. 

The compression and decompression operations are completely transparent to the application and database, and have no performance overhead, even when running at rates of millions of I/Os per second.

Depending on the user data compressibility, Oracle Exadata Storage Server Software dynamically expands the flash cache size up to two times. 

Compression benefits vary based on the redundancy in the data.

  • Tables and indexes that are uncompressed have the largest space reductions. 
  • Tables and indexes that are OLTP compressed have significant space reductions. 
  • Tables that use Hybrid Columnar Compression have minimal space reductions. 
Oracle Advanced Compression Option is required to enable flash cache compression.

This feature is enabled using below CELLCLI command.

ALTER CELL flashCacheCompress=true;

Minimum hardware: Exadata Storage Server X4-2L Servers

What Is Cell Server Disk Scrubbing in Exadata ?

The aim behind disk scrubbing is to repair bad sector of the disk automatically while system is in idle state without compromising the performance. Oracle Exadata Storage Server Software automatically inspects and repairs hard disks periodically when the hard disks are idle.

The default schedule of scrubbing is every two weeks.

Once a hard disk starts to develop bad sectors, it is better to scrub that disk more frequently because it is likely to develop more bad sectors.

In release, if a bad sector is found on a hard disk in a current scrubbing job, Oracle Exadata Storage Server Software will schedule a follow-up scrubbing job for that disk in one week. 

When no bad sectors are found in a scrubbing job for that disk, the schedule will fall back to the scrubbing schedule specified by the hardDiskScrubInterval attribute.

If the user has changed the hardDiskScrubInterval to less than or equal to weekly, Oracle Exadata Storage Server Software will use the user-configured frequency instead of the weekly follow-up schedule even if bad sectors are found. 

How to set interval for disk scrubbing?

The ALTER CELL hardDiskScrubStartTime command sets the start time for proactive resilvering of latent bad sectors. Valid options are a date/time combination or now.


CellCLI> ALTER CELL hardDiskScrubStartTime='2013-08-07T21:19:22-07:00'
The ALTER CELL hardDiskScrubInterval command sets the interval for proactive resilvering of latent bad sectors. Valid options are dailyweekly, biweekly and none. Using the none option stops all disk scrubbing.


CellCLI> ALTER CELL hardDiskScrubInterval=weekly

The following table shows the approximate time needed to scrub one idle hard disk:

In the alert log, you may see messages such as "Begin scrubbing celldisk" and "Finished scrubbing celldisk". These informational messages are expected, and no action is necessary.

If the system is idle, disk scrubbing can drive the disk utilization to 100%. This is expected. Disk scrubbing will throttle itself using IORM based on disk activity. When requests come in, disk scrubbing activity will decrease. Customer workloads should not be affected by disk scrubbing.

1Z0-338 Oracle Exadata Cloud Service 2017 Certified Implementation Specialist

Database-as-a-Service (DBaaS) is an important trend these days and the top business drivers motivating customers towards private database cloud model include constant pressure to reduce IT Costs and Complexity, and also to be able to improve Agility and Quality of Service. 

Since inception Exadata architected for cloud because of its scale out structure , on demand scalability, high performance and superfast network like infiniband. There is no doubt that demand for exadata cloud administrator and implementer will boom in near future. 

To beat the competition you must learn this skill and specially certification will give you added advantages to grow in your professional career. Recently Oracle released beta version of Oracle Exadata Database Machine and Cloud Service 2017 Certified Implementation Specialist which will be in product soon. So GRAB THE OPPORTUNITY TO MAKE A DIFFERENCE by becoming the Exadata Cloud Implementation Specialist.

Exam Number: 1Z1-338 (Beta), 1Z0-338 (Production)
Exam Name: Oracle Exadata Database Machine and Cloud Service 2017 Certified Implementation Specialist

Exam Topics
Oracle Database Software
  • Configure and administer a basic database using Oracle features and functions
  • Tune the Oracle database for performance in common use case scenarios
Oracle Exadata Architecture
  • Describe offloading processing
  • Describe the architecture used by Oracle Exadata software
  • Use Smart Flash Cache
  • Enable Flash Cache Write Back
  • Enable Advanced Compression and Hybrid Columnar Compression on Exadata tables
  • Describe storage indexes
  • Describe Oracle recommended configurations for High Availability configurations
  • Enable parallelism for Data Warehouse workloads
  • Describe database and Automatic Storage Management-Scoped Security Cconcepts
  • Describe the Power Distribution Unit
  • Describe memory capabilities of different models
  • Describe the importance and use of In-Memory Fault Tolerance in the Exadata Database Machine
  • Explain the differences between the types of storage servers available on the Exadata Database Machine
Administration and Configuration 
  • Compress data using Advanced Compression and Hybrid Columnar Compression
  • Use network configuration options
  • Create and configure Automatic Storage Management disk groups using Exadata
  • Explain the impact of various diskgroup failure group choices
  • Install software onto the Exadata Database Machine
  • Describe various tasks that can be done with the Integrated Lights Out Management (ILOM) console
  • Reconfigure a 1/8th rack into a 1/4 rack
  • Describe network components in Exadata
  • Create a database snapshot on Exadata for testing purposes
Backup and Recovery
  • Create a backup plan for Exadata
  • Implement recovery procedures on different failure scenarios
  • Describe troubleshooting tasks for backup and recovery processes
  • Describe how the Exadata Storage Servers are backed up internally
High Availability
  • Describe Oracle's recommended guidelines for high availability configurations on Exadata
  • Identify failure scenarios and implement recovery procedures
  • Install high availability software onto the Exadata Database Machine
  • Install an Enterprise Manager Exadata Monitoring plug-in
  • Set up an agent, plugin, and Exadata target for Enterprise Manager Cloud Control
  • Monitor the storage cell using Cell Command Line Interface and Distributed Command Line Interface
  • Describe the purpose and uses for Simple Network Management Protocol (SNMP), Intelligent Platform Management Interface (IPMI) and Integrated Lights Out Management for a DB machine
  • Use osWatcher and iostat to monitor the Database Machine operating system
  • Use exacli and dbcli to monitor storage cells
Software Maintenance
  • Describe software components
  • Locate patches for Exadata
  • Apply Oracle recommendations to the patching process for Exadata
  • Describe the Oracle Configuration Manager
  • Explain how to perform planned maintenance of the Exadata machine
  • Describe how to use the Oracle Exadata Deployment Assistant to create virtual machines on Exadata
Bulk Loading and Migration
  • Use Database File System (DBFS) to perform bulk loading operations
  • Use the ASM Cluster File System (ACFS) to perform bulk data loading operations
  • Configure a Database for staging input data files
  • Use external tables for data loads
  • Describe migration strategies for Exadata
  • Explain Oracle recommendations on how to choose a migration strategy
Resource Management
  • Set up instance caging
  • Manage I/O on Exadata
  • Set up an Automatic Service Request (ASR) on the Database Machine
  • Explain the ASR configuration process
  • Describe implementation requirements for Platinum Support
Exadata in the Cloud
  • Describe the Oracle Exadata Cloud Service provisioning process
  • Configure backup and recovery on the Exadata Cloud Service
  • Administer the Oracle Database on the Exadata Cloud Service
  • Administer the Oracle Database on the Exadata Cloud Machine 

1Z0-070 - Oracle Exadata X5 Administration

Recently Oracle released beta exam for Oracle Exadata Administration based on X5 machine. It may come in production within 2-3 months.

It is right time to clear 1Z0-027 certification before releasing new exam to become an Exadata administrator.

Let's throw some light on the exam details and exam topics.

Exam Number: 1Z1-070 (Beta), 1Z0-070 (Production)
Exam Name:     Oracle Exadata X5 Administrator

Exam Topics

Exadata Database Machine Overview
  • Identify the benefits of using Database Machine for different application classes
  • Describe Exadata Storage Server and the different Database Machine configurations
  • Describe the key capacity and performance specifications for Database Machine
Exadata Database Machine Architecture
  • Describe the Database Machine network architecture and requirements
  • Describe the Database Machine software architecture
  • Describe the Exadata Storage Server storage entities and their relationships
  • Describe how multiple Database Machines can be interconnected and scaled up
Key Capabilities of Exadata Database Machine
  • Describe the key capabilities of Exadata Database Machine
  • Describe the Exadata Smart Scan capabilities
  • Describe the capabilities of hybrid columnar compression
  • Describe the capabilities and uses of the Smart Flash Cache
  • Describe t he capabilities of Columnar Flash Caching
  • Describe the capabilities of the Smart Flash Log
  • Describe the purpose and benefits of Storage Indexes
  • Describe the capabilities and uses of Exadata Snapshot databases
  • Describe Cell to Cell Data Transfer and Exadata Network Resource Management
Exadata Database Machine Initial Configuration
  • Describe site planning requirements for Database Machine
  • Describe the installation and configuration process with the Exadata Deployment Assistant
  • Describe the default configuration for Database Machine
  • Describe supported and unsupported customizations for Database Machine
  • Describe database machine operating system options and configurations
Configure Exadata Storage Server
  • Configure Exadata software and resources using Cellcli or other tools
  • Create and configure ASM disk groups using Exadata
  • Use the CellCLI, ExaCLI, DCLI and ExaDCLI Exadata administration tools
  • Configure Exadata Storage Server security
I/O Resource Management
  • Use Exadata Storage Server I/O Resource Management to manage workloads within a database and across multiple databases
  • Configure database resource management plans and profiles
  • Configure category plans
  • Configure inter-database plans
  • Describe and configure the I/O resource manager objectives
  • Monitor I/O using I/O Metrics
Recommendations for Optimizing Database Performance
  • Optimize database performance in conjunction with Exadata Database Machine
  • Optimize Cell performance for Flash Cache and latency capping
  • Monitor and configure table indexes, accounting for the presence of Exadata
Using Smart Scan
  • Describe Smart Scan and the query processing that can be offloaded to Exadata Storage Server
  • Describe the requirements for Smart Scan
  • Describe the circumstances that prevent using Smart Scan
  • Identify Smart Scan in SQL execution plans including smart joins
  • Use database statistics and wait events to confirm how queries are processed
Consolidation Options and Recommendations
  • Describe the options for consolidating multiple databases on Database Machine
  • Describe the benefits and costs associated with different options
  • Identify the most appropriate approach for consolidation in different circumstances
Migrating Databases to Exadata Database Machine
  • Describe the steps to migrate your database to Database Machine
  • Explain the main approaches for migrating your database to  Database Machine
  • Identify the most appropriate approach for migration in different circumstances
Bulk Data Loading 
  • Describe the various options for staging data to be bulk loading into Database Machine
  • Configure the Database File System (DBFS) feature for staging input data files
  • Use external tables based on input data files stored in DBFS to perform high-performance data loads
Exadata Database Machine Platform Monitoring
  • Describe the purpose and uses of SNMP for the Database Machine
  • Describe the purpose and uses of IPMI for the Database Machine
  • Describe the purpose and uses of ILOM for the Database Machine
Configuring Enterprise Manager Cloud Control 12c  to Monitor Exadata Database Machine
  • Describe the Enterprise Manager cloud Control architecture as it specifically applies to Exadata Database Machine
  • Describe the placement of agents, plug-ins and targets
  • Describe the discovery process and post discovery configurations
Monitoring Exadata Storage Servers
  • Describe Exadata Storage Server metrics, alerts, Thresholds and active requests
  • Describe and use Exedata Storage Server Quarantines, Disk Scrubbing and repair
  • Monitor Exadata Storage Server using Command line or Cloud control
Monitoring Exadata Database Machine Database Servers
  • Describe the monitoring recommendations for Exadata Database Machine database servers
  • Use Cloud Control or DBMCLI to monitor Exadata Database Machine Database Servers
Monitoring the InfiniBand Network
  • Monitor InfiniBand switches With Cloud Control or CLI
  • Monitor InfiniBand switch ports
  • Monitor InfiniBand ports on the database servers ajd Cells with LIST IBPORT command
  • Monitor the InfiniBand subnet master location
  • Monitor the InfiniBand network topology
Monitoring other Exadata Database Machine Components
  • Monitor Exadata Database Machine components: Cisco Switch, Power Distribution Units
Monitoring Tools
  • Use monitoring tools: Exachk, ExaWatcher, TFA Collector DiagTools, ADRCI, Imageinfo and Imagehistory, OSWatcher
Backup and Recovery for Exadata Database Machines
  • Describe how RMAN backups are optimized using Exadata Storage Server
  • Describe the recommended approaches for disk-based and tape-based backups of databases on Database Machine
  • Describe the recommended best practices for backup and recovery on Database Machine to  Exadata and non-Exadata storage
  • Perform backup and recovery
  • Connect a media server to the Database Machine InfiniBand network
Database Machine Maintenance tasks
  • Power Database Machine on and off
  • Safely shut down a single Exadata Storage Server
  • Replace a damaged physical disk on a cell
  • Replace a damaged flash card on a cell
  • Move all disks from one cell to another
  • Use the Exadata Cell Software Rescure Procedure
Patching Exadata Database Machine
  • Describe how software is maintained on different Database Machine components
  • Describe the recommended patching process for Database Machine with patchmgr, oplan and dbnodeupdate utilities
Database Machine Automated Support Ecosystem
  • Describe the Auto Service Request (ASR) function and how it relates to Exadata Database Machine
  • Describe the implementation requirements for ASR
  • Describe the ASR configuration process
  • Describe Oracle Configuration Manager (OCM) and how it relates to Exadata Database Machine

1Z0-070 Oracle Exadata Exam Dumps

The Most Valuable IT Certification Skill - Oracle Exadata

Recently gone through the foote survey on top demanding IT certification skill by employer. Oracle Exadata certification is one of the hottest certification among them and it is the only from Oracle certification portfolio. If you're looking to improve your skills and possibly your salary, you should go with market trend.
Foote’s rankings are based on data from than 2,600 employers. Value is determined by cash premium, or money that is added to a paycheck in the form a bonus.

Using a bonus, instead of a salary increase, gives employers the flexibility to shift money around as demands for certain skills rise and fall, Foote said.

Foote’s list of the top 10 non-certified skills:

Non-certified skills reflect actual market demand by employers.
  1. JavaFX
  2. SAP BODI (Business Objects Data Integrator)
  3. Business performance management (software/systems)
  4. SAP GTS (Global Trade Services)
  5. Predictive Analytics and Modeling
  6. Oracle Exadata
  7. Scrum
  8. SAP FI - FSCM (Financial Supply Chain Management)
  9. SAP MM (Materials Management)
  10. Mobile operating systems
You can follow our Oracle Exadata Certification Exam Material to achieve maximum success in your Exadata certification.

VNC Server Blank Gray Screen - Exadata Linux

Recently faced issue of VNC server while we have upgraded exadata operating system. 

We have installed VNC server manually on compute node and tried to start the VNC server. Well, it was starting without any issue but it was giving only gray screen without console output. When we have checked VNC server log file, it was showing  below error.

Log file: /home/oracle/.vnc/

/root/.vnc/xstartup: line 28: xterm: command not found

This error is indicating that xterm rpm is missing. After installing xterm rpm everything was working fine.

Related errors if respective RPMs are not installed.

/root/.vnc/xstartup: line 27: xsetroot: command not found
/root/.vnc/xstartup: line 29: twm: command not found

What Is Exafusion ?

Exafusion allows database processes to read and send Oracle Real Applications Cluster (Oracle RAC) messages directly over the Infiniband network bypassing the overhead of entering the OS kernel, and running the normal networking software stack.

  • Lower latency
  • Improve response time
  • Higher throughput direct to wire block transfers between Oracle Real Application Clusters (Oracle RAC) instances
  • Reduced CPU utilization and better scale-out performance
  • Exafusion is especially useful for OLTP applications because per message overhead is particularly apparent in small OLTP messages. It helps small messages by bypassing OS network layer overhead. 

  • EXAFUSION_ENABLED parameter is used to enable or disable the Exafusion accelerate cache fusion protocol feature, which is available on the Linux operating system of Oracle Exadata Database Machine only.
  • Exafusion is disabled by default.
  • To enable Exafusion, set the EXAFUSION_ENABLED initialization parameter to 1. To disable Exafusion, set the EXAFUSION_ENABLED initialization parameter to 0.
  • This parameter cannot be set dynamically. It must be set before instance startup.

Prerequisites and Limitations
  • Oracle Storage Server Software release or later is required.
  • Mellanox ConnectX-2 and ConnectX-3 Host Channel Adapters (HCAs) are required.
  • Oracle Unbreakable Enterprise Kernel 2 Quarterly Update 5 (UEK2QU5) kernels (2.6.39-400.2nn) or later are required.
  • The Exafusion feature does not support mixed mode operation on an Oracle RAC cluster. Either all the instances in an Oracle RAC cluster must have the feature enabled or none.
  • Rolling upgrades of a non-Exafusion enabled Oracle RAC cluster to Exafusion are not supported.
  • Exafusion is available only on the Linux operating system of Oracle Exadata Database Machine
  • It is not supported on any non-engineered system or SPARC Super Cluster (SSC). If you set the EXAFUSION_ENABLED parameter on a non-supported platform, then the instance will be prevented from starting up, and an ORA-00439: The specified feature is not enabled: string error message is generated.
  • This initialization parameter is available starting with Oracle Database 12c Release 1 ( Bundle Patch 11 (BP11).

What is Cell Efficiency Ration in Exadata?

If you have observed, when we invoke CELLCLI utility, it use to display Cell Efficiency Ratio in banner. Example given below.

So what does cell efficiency ratio indicate?

It is the ratio between data accessed by the storage cell and data processed by the database for the cell. Higher the value greater the I/O savings as a result of offloading.

The Cell Efficiency Ratio is same as the value displayed for offloadEfficiency in CELLCLI>LIST CELL DETAIL as below

Then the ratio of the total MB accessed on the cell to the MB accessed on the host (for the cell) is computed every minute that CELLSRV is active by Management Server (MS). 

It is difficult to explain as there is no manual intervention we can do nor we can fetch detailed result of it. We can use it for reference purpose only as there is no practical value from performance perspective of Exadata.