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Fall 2012 ITEC 450 MODULE 3: WEEK 6 DATABASE MANAGEMENT 1 ACCESS DATABASE – SQL PLUS Fall 2012 ITEC 450 2 SQL PLUS LOGIN Fall 2012 ITEC 450 3 SQL PLUS COMMANDS Fall 2012 ITEC 450 4 OEM (HTTPS://{HOSTNAME}:1158/EM) Fall 2012 ITEC 450 5 THE DATA DICTIONARY Fall 2012 Looking at Data Dictionary Components Using Data Dictionary Views Useful Dynamic Performance Views Examining Table Structure Using SQL*Plus and iSQL*Plus ITEC 450 6 LOOKING AT DATA DICTIONARY Fall 2012 ITEC 450 7 LOOKING AT DATA DICTIONARY ITEC 450 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 Fall 2012 8 USING DATA DICTIONARY VIEWS Frequently used (static) data dictionary views: Fall 2012 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 ITEC 450 9 USEFUL DYNAMIC PERFORMANCE VIEWS Begin with V$ and have a counterpart GV$ view ITEC 450 V$SYSSTAT V$SQL V$SESSTAT V$SESSION_WAIT V$FILESTAT V$FILESTAT Fall 2012 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 10 Fall 2012 ITEC 450 MODULE 3 DATABASE MANAGEMENT 11 Section 1 Database Change Management DRIVERS FOR CHANGE MANAGEMENT Fall 2012 ITEC 450 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 12 CHANGE MANAGEMENT REQUIREMENTS ITEC 450 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 Fall 2012 13 TYPES OF DATABASE CHANGES ITEC 450 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 Fall 2012 14 IMPACT OF DATABASE CHANGES Fall 2012 ITEC 450 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. 15 EXECUTION OF DATABASE CHANGES 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 ITEC 450 Maintain current database structures – source control and version control Migration process Fall 2012 16 EXAMPLES OF DATABASE CHANGES Fall 2012 ITEC 450 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 17 Fall 2012 ITEC 450 MODULE 3 DATABASE MANAGEMENT 18 Section 2 High Availability Requirement and Architecture DRIVERS OF AVAILABILITY Fall 2012 ITEC 450 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 19 AVAILABILITY PROBLEMS Server infrastructure problems: network , loss of the server hardware, storage, operating system Software failure: DBMS, application, corruption of data Data ITEC 450 loss of the data center System failures Fall 2012 Disasters: failures Procedure problems: security and authorization, loss of database objects Human errors: loss of data, DBA mistakes 20 AVAILABILITY SOLUTIONS Fall 2012 ITEC 450 Automate DBA functions Exploit high-availability DBMS features Exploit clustering technology Hardware redundancy design 21 HIGH AVAILABILITY DBMS FEATURES Solutions to disasters Solutions to system failures ITEC 450 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 Fall 2012 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 22 CLUSTERING TECHNOLOGY ITEC 450 Oracle standby database: Fall 2012 A cluster is a group of interconnected servers for increasing the reliability of servers. 23 ORACLE REPLICATION Fall 2012 ITEC 450 24 SQL SERVER DATABASE MIRRORING Fall 2012 ITEC 450 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). 25 Fall 2012 ITEC 450 SQL SERVER TRANSACTIONAL REPLICATION ARCHITECTURE 26 ORACLE REAL APPLICATION CLUSTER (RAC) Fall 2012 ITEC 450 Oracle database with RAC architecture build higher levels of availability on top of the standard Oracle features. 27 HARDWARE REDUNDANCY DESIGN Fall 2012 ITEC 450 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 28 RAID TECHNOLOGY Fall 2012 ITEC 450 RAID example with 4 disks and striping. Pages 1-4 can be read/written simultaneously 29 WRAP UP Assignment 6-1: Research Paper: Database High Availability Fall 2012 ITEC 450 30