Download Week 6

Fall 2012
ITEC 450
MODULE 3: WEEK 6
DATABASE 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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THE DATA DICTIONARY
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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
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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:
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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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USEFUL DYNAMIC PERFORMANCE VIEWS
Begin with V$ and have a counterpart GV$ view
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V$SYSSTAT
V$SQL
V$SESSTAT
V$SESSION_WAIT
V$FILESTAT
V$FILESTAT
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Primary use: tuning the database system
 Oracle provides options for gathering/viewing
stats
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Statistics are used to tune a database
 This book does not cover the details of DB tuning
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MODULE 3
DATABASE MANAGEMENT
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Section 1 Database Change Management
DRIVERS FOR CHANGE MANAGEMENT
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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
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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
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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
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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
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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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Maintain current database structures –
source control and version control
Migration process
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EXAMPLES OF DATABASE CHANGES
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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 MANAGEMENT
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Section 2 High Availability Requirement and
Architecture
DRIVERS OF AVAILABILITY
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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
Server infrastructure problems: network , loss of the
server hardware, storage, operating system
 Software failure: DBMS, application, corruption of data
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loss of the data center
 System failures
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 Disasters:
failures
Procedure problems: security and authorization, loss of
database objects
 Human errors: loss of data, DBA mistakes
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AVAILABILITY SOLUTIONS
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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
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Solutions to system failures
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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
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Oracle Real Application Clusters
SQL Server transactional replication
DB2 Data Sharing
Solutions to data failures
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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
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Oracle standby database:
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A cluster is a group of interconnected servers for
increasing the reliability of servers.
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ORACLE REPLICATION
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SQL SERVER DATABASE MIRRORING
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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)
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Oracle database
with RAC
architecture
build higher
levels of
availability on
top of the
standard Oracle
features.
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HARDWARE REDUNDANCY DESIGN
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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
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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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