At High level, business continuity plan, often abbreviated as BCP ,is a plan consisting of action items , critical information pertaining to key resources, infrastructure or other key attributes of a business to ensure that the business stay running even in the unfortunate conditions / disasters. It not only states the business essential functions but also prioritize various processes that must be recovered in order to run the business.
Business continuity plan is important for any business. It not only focuses on resuming the business after an unfortunate situation but also ensure the functioning and delivery of product and services to the customers during such events.
BCP is important for any organization as any organization cannot ignore following risks to the business:
Natural disaster
Accidents
Power and energy failures
Cyber attacks
Environment disasters
With the advent of internet, business have changed and got a lot more dependent on the IT services. Businesses like Amazon, ebay , which are entirely web based cannot afford down time in case of any disaster or cyber-attack. With increasing dependence on IT services, it has become utmost important to ensure that IT services holds an important position in any business continuity plan.Any down time in the services to the customers is directly paired with the revenue stream so IT services plays a significant role in a business continuity plan. Failures in IT services can range from a database failure, network failure, power outage or server crashes etc.
Even though business continuity plan depends largely on the type of business, a good business plan must consist of:
Contact information of POCs (Point of contact) Resources from respective department, as required.
List of critical operations of the business.
Any incident that could interrupt an enterprise business should be addressed by a business continuity plan
A strategy for uninterrupted supply and procurement chain in case of any unfortunate condition.
A strategy for secure transmission of information from one business site to another.
A strategy for human resources to be able to continue doing their jobs in case of any such event.
List of alternate means of communication, if communication media goes down.
It must be tested and updated time to time.
At high level, Business continuity planning process involves following:
BCP governance
Business Impact analysis.
Plans and measures to recover
Readiness procedures.
Quality assurance techniques
Discuss some of the types of failures that can occur with a Database Management System (DBMS) and how those failures might occur. It is not necessary to delve too deeply into how to resolve those failures at this point as we will discuss this in more depth as the weeks go by.
As any other system, Database management systems are prone also to failures. Failures to DBMS can be catastrophic to any application as it handles the data for the applications. With a DBMS failure, Applications fails to resume normal functioning so it utmost important to identify and recover DBMS failures. Although, DBMS failures can be of any kind and can happen due to numerous reasons , failures can be classified in to following categories, at high level.
System Failures : The factors ,which are outside the System and cause systems to fail such as :
Power outage
Hardware or software failures
Operating system failures
Media Failure: With the advancement in technology over last many years, these type of failures have gone low in occurrence. For the purpose of our discussion these failures can occur due to following
Hard disk failures.
Disk not accessible
Disk head crash
Bad sectors on the disk due to which data on the disk become inaccessible.
Transaction Failure: Transactional failures does not impact the system as a whole; Transaction failures cause the given database transaction to fail wherein the transaction fails to execute successfully. This can happen due to following:
Logical errors : Logical errors are the errors present in the code, transactions cannot be completed due to code error.
System Errors : System errors can be any errors where the database system terminates due to some condition. This condition can be unavailability of sufficient resources to execute the process or it can be a condition such as dead locks.
Natural Disasters: These types of failures are unavoidable and occur due to natural calamity. It can lead to physical damage to data , or complete loss of data.it can happen due to:
Flood, earthquake, tornadoes, cyclones etc.
Physical loss of data.
we need to understand the physical, logical and memory structures of an Oracle database. Please provide brief discussions of these topics and how they are related to backup and recovery.
Oracle has physical, logical and memory structures that are used to manage the data stored in database. This layered architecture helps oracle to manage data in one layer without affecting the other layer. For example: Renaming a database file , which is stored in physical storage, does not change the name of the table, which is part of logical structure. It is very important to understand the memory architecture of oracle database or any database to be able to effectively implement any back and recovery strategy. We will briefly go through these layers in order understand them better:
Physical Storage structure layer of oracle database mainly consists of
Data files and temp files- Data file is actual file stored on the hard disk and it contains actual data of tables and indexes. A temp file is also an actual physical file on the system but it can only be read by oracle and is used for temporary purposes by oracle database.
Control files: is the file which contains the information about the physical components of the oracle database.
Online redo log file: Log file contains the information pertaining to the changes done in the data.
Logical storage structure layer of oracle database maintains logical hierarchy of data stored in the oracle database. At high level, following are the logical units of the database:
Data blocks : are the smallest units used for data storage. Oracle stores data in data blocks. One data block refers to a given number of physical storage or bytes to store data.
Extents : is set if continuous data blocks used for storing information.
Segments : is set of extents used for a given database object such as table or indexes.
Table spaces : each table space can have one or more segments but each segment belongs to only one tablespace.
Memory structure of oracle database is a memory area , which is used for any request processing by the oracle database. This memory is used for Program code, maintain sessions, information needed to execute a query,cached data etc. Following are the basic memory structure used by oracle database:
System global area: contains data and control information for one oracle database instance. This is shared memory area that is used to store any cached information or shared sql information.
Program global area: This memory area is exclusively used by single process and is not shared among different processes. It contains data and control information related to given process or program.
User global area: Memory associated with each user session is called user global area.This may contain any user specific information such preferences etc.
Software code area: Is a memory area used to store a software code that can be reused later.
Now , since we have briefly discussed the storage structures of oracle database let’s talk a little about the backups. Database backup can be of following types:
Physical backups: as the name suggests, are copies of physical files associated with the database.
Logical backups: contain logical data such as tables and stored procedures. Logical backups are generally slower than physical backups but offer more transportability.
Whole database backup : is backing up every data file associated with the database and the control files.
Partial database backup : is backing up only subset of the database . For example backing up a single tablespace.
Consistent database backups: when all the backup files have same checkpoint, which guarantees that all files contain data up to a certain point.
Inconsistent database backups: in this type of backup, all files may not contain data up to a common shared check point. Any online back or hot back are generally inconsistent because changes are made when the database is being backed up.
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