The following query returns the control file information about the redo log for a database. That is, one more standby redo log file for each thread. The following views provide information on redo logs. The oracle instances in real application clusters write data onto the asm to update the control file, server parameter file, each datafile, and each redo log file. At the time of drop the redo log file you got error, because till the time archeiver didn write the redo log file. First you should switch the log file using this command alter system switch logfile. Oracle 10g r2 database redo log files oracle community. Asm is not a generalpurpose filesystem and can be used only for oracle data files, redo logs, and control files. I need to set my redo log file to use 200mb to each group. In an oracle rac database, each instance must have at least two groups of redo log files. How to add or increase the size of redo log files in rac. If you use asm to store the archived redo logs for your oracle rac database, then each instance automatically has access to all the archived log files generated by the database. In highupdate databases, no amount of disk tuning may relieve redo log bottlenecks, because oracle must push all updates, for all disks, into a single redo location. I have been trying to understand the concept of redo log threads in a rac environment.
I understand how the redo logs work in a single instance database. How can delete the redo log file alter database add std logfile group 4 u01app oracle oradata orclredo0 4. Oracle redo log is the most crucial structure for recovery operations, redo logs consists of 2 or additional preallocated files that store all changes made in database as they occur. If you want resize the redo log file, you should drop the current log file. After software installation, you are advised to adjust the redo log file size to a value. See managing archived redo logs for more information lgwr writes to redo log files in a. Managing security, users, roles, privileges, profile management. You must move all oracle database files, control files, redo log files, archived redo log files to a shared storage location on a shared filesystem before you start the rac migration process. Log file checking starts from software installation and continue through out life of database. A redo record, also called a redo entry, holds a group of change vectors, each of which describes or represents a change made to a single block in the database for example, if a user updates a. To see the names of all of the member of a group, use a query similar to the following. You must allocate the redo log groups before enabling a new instance. Oracle real application clusters is a database clustering solution that allows more than one instance to mount and open an oracle database. The oracle provided cluster ready services crs need voting disks and ocr files.
About putting the oracle rac database instances into the correct state. Asm provides some filesystem and volume management capabilities for oracle database files only. Shayne capo senior database administrator opera global technical services opera global technical services opera global technical services oracle architectural components opera global technical services architectural components there are several files, processes and memory structures in an oracle server. Rac on windows 10g oracle applications step by step. Rac can only be used on special clustered systems with shared disk storage and a private network interconnect a normal oracle installation consists of a single oracle instance that accesses a database on the same. When you use dbca to create the database, dbca allocates redo log files to instances, as required, automatically. Managing the redo log oracle dba redo log management. Recovering after the loss of online redo log files. Every oracle database must have at least 2 redo logfile groups. This is done because oracle performs deferred batch writes i. After we created primary and standby dbs we realize what we havent put file names as per our standard. Anyone who knows anything about database administration knows the importance of the. How to resize the online redo logfiles oracle rac dba. Hussam uddin ocp application databse administrator ibm.
This oracle documentation was created as a support and oracle training reference for use by our dba performance tuning consulting professionals. In oracle 10g, oracle provides its own storage management with a new feature called automatic storage management asm. Oracle clusterware software is designed to run oracle in a cluster mode, it can. General guideline for sizing the online redo log files mosc id 781999.
The redo log stores a copy of the changes made to data. Performing backups of your oracle real application clusters database. How to resize online redo log files in rac database with. If status is blank for a member, then the file is in use. Configuration of sap netweaver for oracle database 10g.
Oraclebase oracle 10g rac on linux using vmware server. Log directory structure in cluster ready services to diagnose any problem, the first thing examined by oracle support are the installation log files. Connect to the standby database, and create the standby redo logs to. Ask tom redo log threads in real application clusters. The redo log file groups of an instance are collectively called a thread.
Before resize each thread was having 3 redo log groups with 1 member of 50mb in each group. Crs log, listener log, oracle log, rac log if you are using rac system doesnt matter how many nodes you have you need to know where log files are located. Real application clusters requires that all each instance be able to access a set of asm devices on a shared disk subsystem. Oracle rac uses the number value of the thread parameter to assign redo log groups to specific instances. We are in process of testing dataguard with physical standby. What matters is the transaction informaiton contained in them not their. The redo log is used to recover a database after hardware, software, or media failure. Installation and configuration of oracle server for single node and rac on unix, linux, solaris and windows platforms on filesystem and asm. However, the recommended number of standby redo log file groups is dependent on the number of threads on the. Could you write something on redo recovery in case one of the redo files from either instances is missing. Somewhere in the documentation it stated that from 10g that redo logs contain text of sql as well as dml. Oracle database 10g and oracle rac 10g over nfs on celerra. The 12c docs note these details on the contents of redo logs.
The database requires a minimum of two files to guarantee that one is always available for writing while the other is being archived if the database is in archivelog mode. Set the redo log size to be larger than 10 gb and assign 10 redo logs for each instance. It is also recommended to have the archive log files destination on a shared file system. If a media failure has affected the online redo logs of a database, then the appropriate recovery procedure depends on the following.
Oracle redo log size increase in oracle 12c techpaste. It assumes that the servers are using a cluster file system and all hardware cluster setup has been completed. When working as remote dba log files plays very important role in day to day monitoring and trouble shooting. First of all, you cant resizing the redo log files. Installing oracle database 10g release 2 on linux x86. When the database is in no archive log mode, redo log files will get overwritten each time all the redo groups are switched and we cannot have backups of those redo logs. Rac tuning for redo logs burleson oracle consulting. Renamingdropping and recreating online redo logs and. Recovering your oracle real application clusters database. In the oracle rdbms environment, redo logs comprise files in a proprietary format which log a history of all changes made to the database.
This article is intended as a brief guide to installing oracle database 10g 10. Rac preparing shared storage required files and directories. Hence, we use archivelog mode, where each logfile gets archived as backups before log writer lgwr overwrites the logfile. Resizing the online redologs on a rac environment is a simple task, that require a little more attention than that of a single instance. How to resize redolog file in oracle one can succeed at. But i cannot find proper documentation anywhere that clearly explains what a redo log thread is and how the whole thing works in a rac setup. This is a total of 10 redo log groups for the database. Oracle 10g archive redo log files oracle community. Most database administrators know that it is good practice to have at least three orl groups for the database. The clusterready services crs is a new component in 10g rac, its is.
There is no harm wit the different sizes of the files. Oracle 10g rac on linux using vmware server test this article describes the installation of oracle 10g release 2 10. See managing archived redo logs for more information lgwr writes to redo log files in a circular fashion. Redo log content format tips oracle consulting, oracle. In my case i have four redo log files and they are of 50mb in size. If a failure requires a data file to be restored from backup, then the recent data changes that are missing from the restored datafile can be obtained from the redo log, so work is never lost. The recovering instance expects the required archive log file names to have the format defined by its own. So in case you have any parameters set to make the switch happen at certain time,depending on the activity of teh database,the archive file size may vary. So i got the task to rename both, online redo logs and standby logs. Waheed, when the redo log switch willbe happening, oracle would be asking archiver to log that into the archive file. Online redo logfile, dedicated for writeread to only one instance, only one instance. All the redo log files supporting the redo groups reside on shared storage so that every instance in the cluster can access all the redo groups during the recovery process. Oracle writes all statements except, select statement, to the logfiles. Oracle real application clusters oracle rac oracle docs.
Oracle rac tutorial oracle rac architecture oracle rac. These include db control files, redo logs, archived redo logs, data files, spfiles and oracle recovery manager rman backup files. The redo log of a database consists of two or more redo log files. If you use shared storage or raw devices to store the archived log files on each node, then you must configure the operating system to grant access to those directories. The redo logs contains only the changes to data ddl and dml statements. Oracle rac is a part of the oracle database 10g release 2 software and is implicitly. Each instance of database change has an associated redo log to guard the info just in case database encounters a failure. The database consists of a collection of data files, control files, and redo logs located on disk. Oracle rac allows multiple computers to run oracle rdbms software simultaneously while accessing a single database, thus providing clustering in a non rac oracle database, a single instance accesses a single database. Upgrade database from two servers rac 10g to four servers rac 11g. Now a days, database is not just a single sw to work upon, real application cluster and automatic storage management has became an integral. How to resize the online redologs on a rac environment.
Build disaster recover site contain two rac server nodes using physical standby. Installing oracle database 10g release 2 on linux x86 rhel4 and sles9 covered. Put all sap subdirectories sapbackup, sapcheck, sapreorg, saptrace, oraarch etc. About preparing to restore and recover your oracle rac database. Where and specify the location and size of log files. Managing control files, data files, redo log files, undo etc. The online redo log orl for oracle rac is slightly different than a singleinstance database. However, you still need to change the oracle network.
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