Skip to main content

RAC ARCHITECTURE



The Oracle Real Application Clusters (RAC) option was first released as part of Oracle 9.0.1 in the summer of 2001. It is considered by many within the Oracle community to be the most significant feature introduced in Oracle 9i.

Oracle Real Application clusters allows multiple instances to access a single data base, the instances will be running on multiple nodes. In an standard Oracle configuration a database can only be mounted by one instance but in a RAC environment many instances can access a single database.


The table below describes the difference of a standard oracle database (single instance) an a RAC environment

Component
Single Instance Environment
RAC Environment

SGA

Instance has its own SGA

Each instance has its own SGA
Background processes
Instance has its own set of background processes
Each instance has its own set of background processes
Datafiles
Accessed by only one instance
Shared by all instances (shared storage)
Control Files
Accessed by only one instance
Shared by all instances (shared storage)
Online Redo Logfile
Dedicated for write/read to only one instance
Only one instance can write but other instances can read during recovery and archiving. If an instance is shutdown, log switches by other instances can force the idle instance redo logs to be archived
Archived Redo Logfile
Dedicated to the instance
Private to the instance but other instances will need access to all required archive logs during media recovery
Flash Recovery Log
Accessed by only one instance
Shared by all instances (shared storage)
Alert Log and Trace Files
Dedicated to the instance
Private to each instance, other instances never read or write to those files.

ORACLE_HOME
Multiple instances on the same server accessing different databases ca use the same executable files
Same as single instance plus can be placed on shared file system allowing a common ORACLE_HOME for all instances in a RAC environment.



Comments

Post a Comment

Popular posts from this blog

Registering The Database to RMAN catalog database:

Registering The Database to RMAN catalog database: Need to start RMAN as follows: RMAN target=sys/password@database_to_backup rcvcat=sys/password@recovery_catalog_database Another variation on the command, if the recovery catalog and the database were on the same server, might be as shown: oraenv ORACLE_SID = [KKUY] ? KKUY RMAN rcvcat=sys/password@recovery_catalog_database RMAN> connect target Recovery Manager: Release 8.0.5.1.0 - Production RMAN-06005: connected to target database: KKUY RMAN-06008: connected to recovery catalog database Use the below command to register the database. RMAN>register database; Want to verify if a database is registered in the recovery catalog. To do this, connect to RMAN and issue the command LIST INCARNATION OF DATABASE. RMAN> list incarnation of database; RMAN-03022: compiling command: list RMAN-06240: List of Database Incarnations RMAN-06241: DB Key Inc Key DB Name DB ID      CUR Reset SCN   Reset Time RMAN
Post a Comment
Read more

ORA-39014: One or more workers have prematurely exited.ORA-00018: maximum number of sessions exceeded

ERROR: I was Performing a full database import and during the import I faced the below error. ORA-39014: One or more workers have prematurely exited. ORA-39029: worker 6 with process name "DW07" prematurely terminated ORA-31672: Worker process DW07 died unexpectedly. Job "SYSTEM"."SYS_IMPORT_FULL_04" stopped due to fatal error at 00:59:40 ORA-39014: One or more workers have prematurely exited. SOLUTION:  Run the import with fewer parallel processes, like PARALLEL=2 instead of 8. I was able to run the import successfully. NOTE 1: This errors occurs when there are less session allocation in the database. check the session,process parameters and increase them accordingly. To avoid such errors again. NOTE 2 : Note: Increasing processes parameter increases the amount of shared memory that needs to be reserved & the OS must be configured to support the larger amount of shared memory. So here we first need to increase the Memory & SG
Post a Comment
Read more