viernes, 6 de noviembre de 2009

ALTA DISPONIBILIDAD

REAL APPLICATION CLUSTERS
Installing Oracle Database 10g with Real Application Cluster (RAC)

To install the RAC database and the instances on all RAC nodes, OUI has to be launched on only one RAC node. In my example I will run OUI on rac1pub.

Use the oracle terminal that you prepared for ssh at Automating Authentication for oracle ssh Logins, and execute dbca. But before you execute dbca, make sure that $ORACLE_HOME and $PATH are set:
oracle$ . ~oracle/.bash_profile
oracle$ dbca

- Welcome Screen: Select "Oracle Real Application Clusters database"
Click Next
- Operations: Select "Create Database"
Click Next
- Node Selection: Click "Select All". Make sure all your RAC nodes show up and are selected!
If dbca hangs here, then you probably didn't follow the steps as outlined at
Automating Authentication for oracle ssh Logins
Click Next
- Database Templates: I selected "General Purpose".
Click Next
- Database Identification:
Global Database Name: orcl
SID Prefix: orcl
Click Next
- Management Option: I selected "Use Database Control for Database Management".
Click Next
- Database Credentials:
I selected "Use the Same Password for All Accounts". Enter the password and
make sure the password does not start with a digit number.
Click Next
- Storage Options: I selected "Automatic Storage Management (ASM)", see
Installing and Configuring Automatic Storage Management (ASM) and Disks
Click Next
- Create ASM Instance:
Enter the SYS password for the ASM instance.
I selected the default parameter file (IFILE):
"{ORACLE_BASE}/admin/+ASM/pfile/init.ora"
Click Next

At this point DBCA will create and start the ASM instance on all RAC nodes.
Click OK to create and start the ASM instance.

An error will come up that oratab can't be copied to /tmp. I ignored this error.

If you get "ORACLE server session terminated by fatal error", then you probably
didn't follow the steps at Setting Up the /etc/hosts File

- ASM Disk Groups: - Click "Create New"

Create Disk Group Window:
- Click "Change Disk Discovery Path".
- Enter "ORCL:VOL*" for Disk Discovery Path.
The discovery string for finding ASM disks must be prefixed with "ORCL:",
and in my example I called the ASM disks VOL1, VOL2, VOL3.
- I entered an arbitraty Disk Group Name: ORCL_DATA1
- I checked the candidate: "ORCL:VOL1" and "ORCL:VOL2" which have
together about 60 GB space in my configuration.
- Click OK.

- Check the new created disk group "ORCL_DATA1".
- Click Next
- Database File Locations:
Select "Use Oracle-Managed Files"
Database Area: +ORCL_DATA1
Click Next
- Recovery Configuration:
Using recovery options like Flash Recovery Area is out of scope for this article.
So I did not select any recovery options.
Click Next
- Database Content: I did not select Sample Schemas or Custom Scripts.
Click Next
- Database Services: Click "Add" and enter a Service Name: I entered "orcltest".
I selected TAF Policy "Basic".
Click Next
- Initialization Parameters:
Change settings as needed.
Click Next
- Database Storage: Change settings as needed.
Click Next
- Creation Options: Check "Create Database"
Click Finish
- Summary: Click OK

Now the database is being created.

The following error message came up:
"Unable to copy the file "rac2pub:/etc/oratab" to "/tmp/oratab.rac2pub".
I clicked "Ignore". I have to investigate this.


Your RAC cluster should now be up and running. To verify, try to connect to each instance from one of the RAC nodes:
$ sqlplus system@orcl1
$ sqlplus system@orcl2
$ sqlplus system@orcl3

After you connected to an instance, enter the following SQL command to verify your connection:
SQL> select instance_name from v$instance;

Referencia: http://www.puschitz.com/InstallingOracle10gRAC.shtml



DATA GUARD


UN MOTIVO MAS PARA CONSIDERAR A ORACLE COMO LA BASE DE DATOS MAS SEGURA Y DISPONIBLE


Es la funcionalidad de la base de datos Oracle que brinda la mayor y más efectiva disponibilidad, protección y recuperación ante desastres de los datos, ya que provee la administración, el monitoreo y la automatización de una o más bases de datos standby para proteger a los datos ante fallas, desastres, errores o corrupción. .
Tanto sea que las bases standby estén ubicadas en un sitio de recuperación ante desastres a varios kms del sitio de producción o en el mismo edificio, esta funcionalidad asegura que si la base de datos de producción sale de servicio, sea de manera planeada como imprevistamente, Data Guard switchea automáticamente la base standby al rol de base de producción, minimizando el tiempo de la caída y previniendo la pérdida de datos.
Data Guard brinda confiabilidad, ya que eladministrador siempre conoce el estado de las bases standby que pueden, en solo segundos, asumir el rol primario
Principales beneficios
a)Recuperación ante desastres y alta disponibilidad
Mediante un failover automático y fácil de administrar que en segundos cambia el rol de las bases de standby a producción
b)La base standby database también provee una salvaguarda efectiva contra la corrupción de los datos y los erroresde los usuarios
Ya que daños físicos en la base de datos primaria no se propagan a la standby
c)La base standby puede ser utilizada para backups y reportes de sólo lectura
Reduciendo la carga de trabajo de las bases productivas ahorrando ciclosde CPU y de E/S.
d)Flexibilidad en la protección de los datos
Balancea la disponibilidad con los requerimientos de performance
e)Protección ante fallas de comunicación
Si la conectividad de la red se pierde, por lo que no se pueden transmitir los datos entre las bases productivas y las standby, luego cuando se reestablece la misma, los datos perdidos son automáticamente detectados porData Guard y los logs de los archivos son transmitidos a las bases standby, lasque se resincronizan con las bases primarias, sin intervención manual del administrador.
f)Administración simple y centralizada
La funcionalidad Data Guard Broker automatiza la administración y el monitoreo detodas las bases de datos
g)Economía
Ya que Data Guard está disponible como una característica integrada de la versión Enterprise Edition sin costo adicional.
Referencia: http://www.kit.com.ar/boletines-a.php?id=0000035


TECNOLOGIA ORACLE FLASHBACK

According to many studies, 40% of application outages are caused by operator or user errors. Part of being human is making mistakes. But these errors are extremely difficult to avoid and can be particularly difficult to recover from without advance planning and the right technology. Such errors can result in "logical" data corruption, or cause downtime of one or more components of the IT infrastructure. While it is relatively simple to rectify the failure of an individual component, detection and repair of logical data corruption, such as accidental deletion of valuable data, is a time consuming operation that causes enormous loss of business productivity. Typical user-errors may include accidental deletion of valuable data, deleting the wrong data, and dropping the wrong table.
Guarding Against Human Errors
The Oracle Database architecture leverages the unique technological advances in the area of database recovery due to human errors. Oracle Flashback Technology provides a set of new features to view and rewind data back and forth in time. The Flashback features offer the capability to query historical data, perform change analysis, and perform self-service repair to recover from logical corruptions while the database is online. With Oracle Flashback Technology, you can indeed undo the past!
Oracle9i introduced Flashback Query to provide a simple, powerful and completely non-disruptive mechanism for recovering from human errors. It allows users to view the state of data at a point in time in the past without requiring any structural changes to the database.
Oracle Database 10g extended the Flashback Technology to provide fast and easy recovery at the database, table, row, and transaction level. Flashback Technology revolutionizes recovery by operating just on the changed data. The time it takes to recover the error is now equal to the same amount of time it took to make the mistake. Oracle 10g Flashback Technologies includes Flashback Database, Flashback Table, Flashback Drop, Flashback Versions Query, and Flashback Transaction Query.
Flashback technology can just as easily be utilized for non-repair purposes, such as historical auditing with Flashback Query and undoing test changes with Flashback Database. Oracle Database 11g introduces an innovative method to manage and query long-term historical data with Flashback Data Archive. This release also provides an easy, one-step transaction backout operation, with the new Flashback Transaction capability.

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