Basic Memory Structures

Refer: http://docs.oracle.com/cd/E11882_01/server.112/e40540/memory.htm#CNCPT7778

The basic memory structures associated with Oracle Database include:

• System global area (SGA)
  The SGA is a group of shared memory structures, known as SGA components, that contain data and control information for one Oracle Database instance. The SGA is shared by all server and background processes. Examples of data stored in the SGA include cached data blocks and shared SQL areas.
• Program global area (PGA)
  A PGA is a nonshared memory region that contains data and control information exclusively for use by an Oracle process. The PGA is created by Oracle Database when an Oracle process is started.
  One PGA exists for each server process and background process. The collection of individual PGAs is the total instance PGA, or instance PGA. Database initialization parameters set the size of the instance PGA, not individual PGAs.
• User Global Area (UGA)
  The UGA is memory associated with a user session.
• Software code areas
  Software code areas are portions of memory used to store code that is being run or can be run. Oracle Database code is stored in a software area that is typically at a different location from user programs—a more exclusive or protected location.

Figure 14-1 illustrates the relationships among these memory structures.

Figure 14-1 Oracle Database Memory Structures

Description of "Figure 14-1 Oracle Database Memory Structures"

Oracle Database Memory Management

Memory management involves maintaining optimal sizes for the Oracle instance memory structures as demands on the database change. Oracle Database manages memory based on the settings of memory-related initialization parameters. The basic options for memory management are as follows:

• Automatic memory management
  You specify the target size for instance memory. The database instance automatically tunes to the target memory size, redistributing memory as needed between the SGA and the instance PGA.
• Automatic shared memory management
  This management mode is partially automated. You set a target size for the SGA and then have the option of setting an aggregate target size for the PGA or managing PGA work areas individually.
• Manual memory management
  Instead of setting the total memory size, you set many initialization parameters to manage components of the SGA and instance PGA individually.

How Devops can be improved?

Few tips to improve Devops:

Frequency of deployments – The number should either remain steady or go up week to week.
Volume of changes – Measure the volume and complexity of user stories and new lines of code deployed.
Amount of time from development to deployment – The lead time from when the code begins development till it’s deployed to production. The amount of time should decline as the team develops – and is a central gauge of how efficient the process is and where it must be improved.
What is the ratio of unsuccessful deployments? – How often do deployments fail or even cause outages? As DevOps is implemented, the quality of the deployments should go up and the percentage of failed deployments should go down.
Recovery Time – This is perhaps the greatest test of the quality of the team – how long does it take to recover when a failure does occur. Although the time should generally trend downwards, teams should not be discouraged by the occasional spike as they run into issues for the first time.
Customer Tickets – The goal of DevOps is to increase deployments without causing failures. By reviewing the number of customer tickets you’ll have a good idea how well you’re doing.
Increase in user volume – By tracking how many users are signing up you can make sure the organization can handle the new requests.
Response Time – This number should remain steady no matter the percentages of change in user volume as the product should be functioning in predetermined thresholds.

Oracle Basic : Oracle 10g vs Oracle 11g

Top few features to list - Difference between 10g and 11g

1.Simplified and improved automatic memory management

2.New fault diagnosability infrastructure to prevent, detect, diagnose, and help resolve critical database errors

3.Invisible Indexes

4.Virtual columns

5.Enhanced security for password-based authentication by enabling use of mixed case in passwords.

6.Tablespace-level encryption

7.Ability to online redefine tables that have materialized view logs

Difference between 11gr1 and 11gr2

Oracle 11gR2 is the second and terminal release of the Oracle 11g database.
The common theme for this release is "Consolidate. Compress. Control.".

New Features:

1. Oracle RAC One Node
2. Improved data compression ratios (up to 20x).
3. Ability to upgrade database applications while users remain online.
4. New ease-of-use features that make Grid computing more accessible.
5. deferred segment creation new feature in Oracle 11gR2
6. In-Memory Parallel Execution
7. Auto Degree of Parallelism (Auto DOP) and Parallel Statement Queuing
8. Significant Performance Improvement of MV On-Commit Fast Refresh
9. Database Resource Manager Instance Caging
10. Hybrid Columnar Compression

(source - internet)