Most database administrators know that it is good practice to have at least three orl groups for the database. The files are written in oracle proprietary format and cannot be read directly. When a redo log group is dropped from the database, and you are not using the oraclemanaged files feature, the operating system files are not deleted from disk. Jeffrey hunter is an oracle certified professional, java development certified professional. Let us we discuss how to resize the redo logfile online redo logfile in oracle 11g. Oracle cloud infrastructure classic 2018 certified architect associate. Resizing the online redologs on a rac environment is a simple task, that require a little more attention than that of a single instance. Dumping redo log file information oracle database 10g. If you have a 100 log switches an hour with 50mb redo logs, you need e. Oct 20, 2017 how to resize the redo logfile online redo logfile in oracle 11g. For dropping an online redo log group, use the alter database statement with. Maa best practices dictates that to avoid such scenarios, we should be multiplexing the online redo log files. Logwriter writes to redo log files in a circular fashion.
Add or drop inactive online redo log files searchoracle. Rac and grid infrastructure administration exam 1z0068 and become oracle certified expert. How to resize redo on rac instance with asm option helioss. Using group numbers can make administering redo log groups easier. To drop the old redo log files need to switch the log file on all the instance until all current online redologs are located on the newly added groups. Rac redo log thread maintenance burleson oracle consulting. Change ip address for oracle rac public and vip interfaces. Renamingdropping and recreating online redo logs and standby logfiles. Oracle grid book rac clusters dba book rampant books. Disabling an old rac instance thread the great grandson. Jan 02, 2008 redo log files are written by redo log writter process. It is not possible to resize the redo log or standby redo log srl dynamically.
If a media failure damages all members of an online redo log group, then different scenarios can occur depending on the type of online redo log group affected by the failure and the archiving mode of the database. Rac tuning for redo logs oracle consulting, oracle. The online redo log orl for oracle rac is slightly different than a singleinstance database. First, i have to drop group 2 because group ones status is current. Tutorial on managing redo logfiles in oracle with step by step examples. After all groups in database are filled it returns back to first redo log group. The information in this guide is not validated by oracle, is not supported by oracle, and should only be used at your own risk. In an oracle rac database, each instance must have at least two groups of redo log files. Mar 05, 20 how to resize redo log and standby redo log in oracle dataguard environment. However, the group number must be between 1 and maxlogfiles.
However there are simple command for reading the logfile. How to add or increase the size of redo log files in rac environment. How to resize redo log and standby redo log in oracle dataguard environment. Find answers to delete redo log from the expert community at experts exchange. Oracle grid and rac is the firstofitskind reference for oracle grid computing. How to droprename standby redolog file in oracle 11g while performing the dataguard broker, we need to drop the standby database while switchover the standby. Loss of a single current online redo log file will require us to restore the entire database and do an incomplete recovery. Because of that, there has to be at least 2 groups in an instance. Mar 22, 2007 redo buffers 6307840 bytes database mounted. Next, here are some examples of how to drop a group or member. For dropping an online redo log group, use the alter database statement with the drop logfile clause. I have 3 redo log group, each group have only one member, is it safe to add a members to each group anytime. How to resize the redo logfile online redo logfile in oracle 11g. How to resize the redo logfile online redo logfile in.
Plan the redo log of a database and create all required groups and members of redo log files during database creation. Archiving of redo log files is necessary for hot online backups, and is mandatory for pointintime recovery. Premature redo log switching in oracle rac stack overflow. Build your own oracle rac 11g cluster on oracle enterprise. Your course of action will depend on other factors you can read about in the. Managing the redolog in oracle11g ampersand academy. Hi tom, on reading oracle document, there information about adding new log group is. Maintaining standby database as rac with active dataguard and a realtime apply feature allows using it for reading, backup, and testing by converting it over to a snapshot standby database and back after the completion. How to resize online redo log files in rac database with asm. There are exception to this rule, suppose, your redo size is high and two log files were filled up quickly. Firstly oracle will never allow you to drop the current online redolog file.
Apr 19, 2010 multiplexing uses groups of redo log files. Continue the above process until all logfile groups are moved to their new disk volumes. Ive lost a member of the current redo log group so i cannot drop it. The recommended log switch frequency is at least once an hour. The following article describes how to create an oracle rac 11gr2 physical standby database with active dataguard realtime apply enabled on linux. Resize redolog file in oracle oracle blog by anar godjaev. Oct 30, 20 this command will drop the redo log group, which is identified by number 6. Execute dbca from command line, it will open the welcome screen for dbca. Oct 23, 2012 how to add or increase the size of redo log files in rac environment. Redo log files are written by redo log writter process. Redo group 3 is active on instance 2 and instance acts as recovery instance once instance 2 is down, therefore redo group 1 is active on instance 2. Oracle recommends an extra group for standbys but im not sure if that means per thread or not. Multiplexing is a way to have a backup of redo log in oracle. This article explains the steps for multiplexing redologs in oracle rac.
Renamingdropping and recreating online redo logs and standby. As part of the tests im using the drop database command, that made a fast and efficient cleanup of all datafiles, redologs and control files in one command. Now the current redo log file will turns into active redo log file which means that file information are written into archive log through arcn once that written process is over an archive log then it turns into inactive redo log file creating group and member in redo log. How to resize the online redo logfiles oracle rac dba. With an oracle rac standby db where the primary has 2 threads of 4 groups of online redo logs, should the standby db have 2 threads of 5 groups each. Nov 29, 2007 especially to benefit from migrations most to remove the cbo parameters and let them to take their version specific default values and then monitor and tune is a better strategy. Dec 21, 2009 redo group 3 is active on instance 2 and instance acts as recovery instance once instance 2 is down, therefore redo group 1 is active on instance 2. Oracle dataguard how to resize redo log and standby redo. Drop and recreate online redolog files oracle dba tips and. Covering all areas of oracle grid computing, this book is indispensable for any oracle dba who is charged with configuring and implementing oracle grid with server blades. Recovering after the loss of online redo log files. Disabling an old rac instance thread the great grandson of.
How to resize online redo log files in rac database with asm option. How to add or increase the size of redo log files in rac. How to resize the redo logfile online redo logfile in oracle. For example, adding groups to a redo log can correct redo log group availability problems. How to resize online redo log files in rac database with. Apr 29, 20 renamingdropping and recreating online redo logs and standby logfiles posted by dbakalyan on april 29, 20 we are in process of testing dataguard with physical standby. Redo log files record changes made to the database and are used by oracle for system crash recovery. In particular the section titled recovering after losing of all members of an online redo log group.
Oracle database cloud service operations certified associate. Each group should have at least 2 members and each member should be located on a different physical disk. How can delete the redo log file alter database add std logfile group 4 u01apporacleoradata orclredo0 4. Jan 30, 2017 today we discuss about archive mode and no archive mode before that we have to remain what is redo log file. Recovering after the loss of all members of an online redo log group. The recommendation is to have log switches occur a few times an hour. Sql alter database drop std logfile group 4 u01apporacleoradata orclredo0 4.
The redo logfile contains the history of changes data in database group. This command will drop the redo log group, which is identified by number 6. If you have two diskgroup, you want to multiplex redo in different diskgroup, you just add redo log desitnation diskgroup. Oct 09, 2014 how to resize online redo log files in rac database with asm option database setup has 2 nodes 11. Add or drop inactive online redo log files searchoracle techtarget. When a redo log group is dropped from the database, and you are not using the oracle managed files feature, the operating system files are not deleted from disk.
You can drop member from a log group only if the group is having more than one. Thatswhy it is recommended to multiplex the redo groups. Actually we cant resize the redo logfiles we have to drop the redo logfile and then recreate the redo logfile again with the new size whatever we want. How do i recreate a deleted logfile on an oracle database. Each database consists of two or more redo log files. Or is just one additional group in one of the threads enough.
Rac tuning for redo logs burleson oracle consulting. Posted in oracle, ractagged disable thread, ora01567, rac, redo log groups6 comments. Usually we do resize when redolog switches happen too frequently. Find redo log members redo log file size redo log status. It is not possible to resize the redo log or standby redo log srl. A group contains a redo log and all of its multiplexed copies. Redo is the most crucial part when we talk about recovery and contains the current transaction details, hence if the data is redo is lost point time recovery is impossible depending on the scenario. So far as i know there is no fix for corrupted online redo log. How to resize the online redologs on a rac environment. Oracle 11g oracle 12c rac oracle standby oracle goldengate mongodb postgresdb linux administration shell scripting sqlscripts wednesday, february 19, 2014 how to adddroprename standby redolog file how to droprename standby redolog file in oracle 11g.
For example, a file might be stored in an inappropriate location. To drop a redo log group, you must have the alter database system. With the group removed, add the group anew in the new location alter database add logfile command. How to manage oracle redo logfiles oracle dba online. Migrate an oracle rac database to new servers with zero downtime.
The source and target databases are 2node oracle rac 11gr2. Mar 02, 2008 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 redo on rac instance with asm option. After recreating an online redo log group, continue to recreate or resize all online redo log groups until all of them are rebuilt. When you use dbca to create the database, dbca allocates redo log files to instances, as required, automatically. Method to drop and recreate online redolog files with 2 members to each group. This is not a strict rule, but generally happens most of the time. Rac redo log thread maintenance burleson consulting. How to find the character set of the oracle database. I had a situation where i wanted to read the blocks of online redo log files. Dec 12, 2015 tuning online redo logs in a rac environment.
Build your own oracle rac 11g cluster on oracle enterprise linux and iscsi, page 3. Drop a redo log group with the sql statement alter database with the drop logfile clause. Basically, we need to add new redolog groups in required diskgroup and drop the old ones. The following statement drops redo log group number 3.
Aug 15, 2007 next, drop the online redo log with the alter database drop logfile group x command. I needed to resize the redo log as it takes about 4 days to do a log switch. It is similar to that of multiplexing in standalone, only change is rac will have threads for node. If i drop group 2 and then add it again with these commands. Oracle database cloud administrator certified professional. Even the db is in archivelog mode you can do nothing if the redo log is corrupted. He has handson experience with realworld production environments, and he has risen in the ranks from a developer to a managing dba. Multiplexing means to keep multiple copies of redo log in different diskgroup. Firstly oracle will never allow you to drop the current. Disconnected from oracle database 10g enterprise edition release 10. However, there are situations where you might want to create additional groups or members. Renamingdropping and recreating online redo logs and.
Recovering from the loss of redo log files in the following post well go through every possible scenario where we loose redo, one by one. What are the possible causes of premature redo log switching in oracle other than reaching the specified file size and executing alter system switch logfile we have a situation where some but not all of our nodes are prematurely switching redo log files before filling up. Jan 10, 2015 how to multiplex redo log files in oracle 11g. It is required that there are at least two groups and in the case of multiple members per group that all members be the same size. I have two groups of redo logs that i want to resize. It is recommend but not required that each group has the same number of. Oracle cloud infrastructure 2018 certified architect associate. Recovering from the loss of redo log files oracle database. Sep 01, 2016 add drop redo log groups in oracle rac. Oracle 11g oce,oracle 12c and oracle 11g opn certified specialist, ocp certified in oracle 9i,10g, 11g and 12c.491 91 654 1464 294 451 1116 789 924 1585 992 1242 1340 1330 1546 1300 167 1109 595 929 1130 186 1472 480 238 735 448 941 1098 797 1454 192 701 1374 1445 1003 1194 608 1247 576