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MODULE 3: WEEK 6DATABASE MANAGEMENT

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ACCESS DATABASE – SQL PLUS

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SQL PLUS LOGIN

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SQL PLUS COMMANDS

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OEM (HTTPS://{HOSTNAME}:1158/EM)

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0THE DATA DICTIONARY

Looking at Data Dictionary Components Using Data Dictionary Views Useful Dynamic Performance Views Examining Table Structure Using SQL*Plus

and iSQL*Plus

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LOOKING AT DATA DICTIONARY

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LOOKING AT DATA DICTIONARY

Generally, USER, ALL, and DBA views are in sets USER_TABLES, ALL_TABLES, DBA_TABLES

Each view has nearly identical columns USER version omits OWNER column; it also

sometimes omits columns to simplify the view V$ and GV$ views are in sets There are few views that don’t begin these prefixes For simplicity, all views (except DBA ones) prefix

public synonyms and public permission to query

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USING DATA DICTIONARY VIEWS

Frequently used (static) data dictionary views: USER_TABLES, USER_VIEWS ALL_DEPENDENCIES USER_ERRORS USER_INDEXES, USER_IND_COLUMNS DBA_SOURCE USER_TAB_PRIVS, ALL_TAB_PRIVS_MADE USER_TAB_PRIVS_MADE DBA_USERS PRODUCT_COMOPONET_VERSION

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0USEFUL DYNAMIC PERFORMANCE

VIEWS

Begin with V$ and have a counterpart GV$ view V$SYSSTAT V$SQL V$SESSTAT V$SESSION_WAIT V$FILESTAT V$FILESTAT

Primary use: tuning the database system Oracle provides options for gathering/viewing

stats Statistics are used to tune a database This book does not cover the details of DB tuning

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MODULE 3 DATABASE MANAGEMENTSection 1 Database Change Management

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DRIVERS FOR CHANGE MANAGEMENT

Change is inevitable but necessary for business survival and success.

Missed a requirement – an existing system is missing a feature

Identified a defect Scalability demand, marketplace changes Policy and politics – process, procedure or

methodology; legislation changes

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CHANGE MANAGEMENT REQUIREMENTS Proactively change – the earlier to make

change, the lower cost to achieve it Planning analysis – intelligently examining

the change whether it is necessary, and planning to do it right the first time

Impact analysis – comprehensive impact and risk analysis

Execution – standardization of procedure, availability consideration, quick and efficient delivery

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TYPES OF DATABASE CHANGES DBMS software – versions and releases for

new features, functions, bug fixes, support models

Hardware configuration – memory, CPU, storage device

Logical and physical design for an application

Physical database structures

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IMPACT OF DATABASE CHANGES

Data Definition Language is mainly used for database changes.

Create, alter, and drop schema objects require exclusive access to the specified object

The change is implicitly committed The change may cause dependent objects

become invalid, which may need to recompile or reauthorize schema objects

Recovery from a database change is challenging, and has to be well-planned.

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EXECUTION OF DATABASE CHANGES

Maintain current database structures – source control and version control

Migration process Request database change Standardized change requests Managing database changes from one

database environment to another Condense a series of changes by comparing

database structures, and migrate the differences

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EXAMPLES OF DATABASE CHANGES

Change Management: planning (necessary?) impacts, and execution (recovery?)

Add a new column to the end of a table Resize a column from char (8) to char (12) Re-create a new package, procedure, or

function Add a new column to the middle of a table

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MODULE 3 DATABASE MANAGEMENTSection 2 High Availability Requirement and Architecture

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DRIVERS OF AVAILABILITY

Availability is the condition where a given resource can be accessed by its consumers.

Mandate for 24x7 availability Shrinking maintenance window Full-time availability: airline reservation

systems, credit card approval Cost of downtime

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AVAILABILITY PROBLEMS

Disasters: loss of the data center System failures

Server infrastructure problems: network , loss of the server hardware, storage, operating system

Software failure: DBMS, application, corruption of data

Data failures Procedure problems: security and authorization,

loss of database objects Human errors: loss of data, DBA mistakes

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AVAILABILITY SOLUTIONS

Automate DBA functions Exploit high-availability DBMS features Exploit clustering technology Hardware redundancy design

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HIGH AVAILABILITY DBMS FEATURES Solutions to disasters

Oracle data guard – a single primary database and one or more standby database

SQL Server database mirroring – a single copy of the mirrored database that must reside on a different server instance, usually on a separate physical server in a different location

Hardware replication: EMC SRDF Solutions to system failures

Oracle Real Application Clusters SQL Server transactional replication DB2 Data Sharing

Solutions to data failures Backup and recovery capability Flashback database: view data at a point-in-time in the past Partition: decompose large tables and indexes into smaller

and more manageable pieces

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CLUSTERING TECHNOLOGY

A cluster is a group of interconnected servers for increasing the reliability of servers.

Oracle standby database:

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0ORACLE REPLICATION

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SQL SERVER DATABASE MIRRORING

Database mirroring maintains an exact copy of the database on the mirror.

It works at the level of the physical log record (by sending the actual log records to the mirror server).

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SQL SERVER TRANSACTIONAL REPLICATION ARCHITECTURE

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ORACLE REAL APPLICATION CLUSTER (RAC)

Oracle database with RAC architecture build higher levels of availability on top of the standard Oracle features.

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HARDWARE REDUNDANCY DESIGN

No single point of failures on CPU, Memory, I/O controller, Network, etc.

Clustered software to failover to another server in seconds

RAID technology (Redundant Arrays of Inexpensive Disks) – one large logical storage unit with a set of physical disk drives

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RAID TECHNOLOGY

RAID example with 4 disks and striping.

Pages 1-4 can be read/written simultaneously

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WRAP UP

Assignment 6-1: Research Paper: Database High Availability

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