Server Administration :: Contents Of Redo Log Files
Feb 1, 2011
I have some doubts about redo log files,
1) Can we fetch 'select statements' from redo log files through the use of log miner utility or any other?
(I think redo log file contains only insert,update,delete and DDL/DCL commands only)
2) If "No" to the above answer then how can i fetch all select statements fired on the system for a day or particular time.
(setting of sql_trace may be the one of them, but can it be possible for system level)
alter session set events 'immediate trace name treedump level 51786'
/u01/app/oracle/admin/oracl/udump/oracl_ora_2679.trc Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Production With the Partitioning, OLAP and Data Mining options ORACLE_HOME = /u01/app/oracle/product/10.2.0/db_1
I have oracle 9i running on HP-UX, I would like to find how much redo we are generating in a given period of time, is there any script that I can use to get this information?
I learnt that logWriter writes in the redo log files when redo log buffer is 1/3 full, it means that 66 % of redo log buffer are always empty and never used,
if no, isn't a waste of memory (66 % always empty !)
I've a situation where I've very less redo logs generated. Let us say 10MB. Which solution will be better ?
1. Create one redo log group about 12 MB in size. 2. Create two redo log groups about 5 MB each in size as recommended by Oracle.
Even though solution 1 is also appropriate for me because I've less redo generated than the redo log group size. My whole redo will fit in this and I can raise checkpoint forcefully after certain period of time let us say every 3 seconds.
In one of our DB I found scenario one is implemented. So I want to know pros and cons of both of these practices.
Today i noticed one problem with my database,my redologs switches in every 3mins,i also noticed there is no more transaction changes happening in database but still redo switches.
Fri Oct 05 06:10:05 2012 Thread 1 advanced to log sequence 79244 Current log# 2 seq# 79244 mem# 0: D:ORADATAORACIREDO02.LOG Fri Oct 05 06:12:16 2012 Thread 1 advanced to log sequence 79245 Current log# 1 seq# 79245 mem# 0: D:ORADATAORACIREDO01.LOG Fri Oct 05 06:14:28 2012 [code]......
why redo switch happening,any internal problem causes redo to switch .
redo generation. As I found the below statement in another forum."Undo segment generates the redo data also, because undo segment is database changes, so it generates the redo data also."
How a Undo segment can generate Redo and Undo datas.
Redo is getting generated very high. how to find out the reason ? database kept under 2 node cluster. chcked alert log trace and log writer trace files. pasted the content as below:
--alert log trace from node1 ( node2 also has same type of message ). Archive destination disk group - TXCOM_BACKUP_01 having enough space ( 80gb )
Mon Jan 7 00:49:10 2013 Thread 1 advanced to log sequence 448546 (LGWR switch) Current log# 1 seq# 448546 mem# 0: +TXCOM_DATA_01/txcom/onlinelog/group_1.274.785770579 Current log# 1 seq# 448546 mem# 1: +TXCOM_DATA_01/txcom/onlinelog/group_1.302.802265189 Mon Jan 7 00:49:10 2013
[code]...
In the alert log, I am able to see the archive destination disk group ( TXCOM_BACKUP_01 ) is getting DISMOUNTED and again getting MOUNTED during every archive file generation. .
Mon Jan 7 00:49:20 2013 SUCCESS: diskgroup TXCOM_BACKUP_01 was mounted SUCCESS: diskgroup TXCOM_BACKUP_01 was dismounted SUCCESS: diskgroup TXCOM_BACKUP_01 was mounted SUCCESS: diskgroup TXCOM_BACKUP_01 was dismounted
archive destination parameter in both nodes are not configured. it should read diskgroup name. ( +TXCOM_BACKUP_01 ) and corresponding size limit. Should i configure this ?
SQL> show parameter db_recovery
NAME TYPE VALUE ------------------------------------ ----------- ------------------------------ db_recovery_file_dest string db_recovery_file_dest_size big integer 0
[code]...
should i bring the database to mount stage and set log_archive_max_proesses to high count ? now value is 2 ( default )
SQL> update t set a = 1 where b = 2; -- must have redo record 2 rows updated. SQL> rollback;
the above redo record that uncommit changed must be written from redo buffer to the online redo logfile. why Oracle write the redo record that uncommit changed to the online redo logfile ? when it will be used?
We had our production database hosted on Oracle 9.2.0. Few months back we have migrated it to Oracle 10.2.0.4.0. After Migration I have noticed that redo generation has become very very high. In earlier case no. of log files generating in production hours were around 30 where as after migration it become around 200 files per day. I have run statspack report on this database. Report is saying that db block change & disk write is become very high. Parameter timed_statistics has also been set to FALSE. Even then there is not any reduction on no. of log file generation. I had used import export for upgrading the databases.
Whenever any transaction happen in database redo has generated for this transaction. Do select statement treat as a transaction as it doesn't modify any thing in database. And If select statement should not be a transaction, there should not be any redo generation for select statement.
So is select statement generate redo? If yes then Why ?
understanding a redo/undo concept . Refer following data
create table t(n number); insert into t values(10); commit;
now I update as following
update t set n=20;
As per my understanding the before image i.e. n=10 is stored in undo (to be used for rollback, transaction recovery and even in instance recover but not in media recovery) and after image n=20 is stored in redo (to be used for various recovery purposes including media recovery in case of consistent backup).
So it is redo logs for rolling forward and undo for rolling back making transaction, db consistent . If my above understanding is true then what is meant by the term 'redo required for undo'?
Also, if there are 2 database db1 and db2 connected using database link where we are populating t1 table in db1 using t2 table in db2 using db link where redo and undo will be updated db1 or db2?
I am creating database instance from template. I have specified the location of redo log files. When I run the dbca utility it does creates the redo log files in specified directory. But the installation fails . When I checked the trace file. it says unable to locate the specified file(redo.log). But when i check in directory they are created.
I learned that Oracle uses supplemental logging mechanısm to add the changed rows to redo log files and identify the changed rows on target replication database? Is that mechanism mandatory to handle the replication of data between updated and back up databases?
We have one primary oracle database 10.2 and standby by database with no data guard. Initially we have 2 redo log group in primary and standby database.
We have recently add 2 more redo log and increase the size of log member from 50m to 200m in primary database. We don't have any problem in primary database.but in standby database we face a problem because we cannot open it. It always in mount stage in which . How we change the size of current redo log because we can't run. Alter system switch logfile command in mount stage.
In the backup and recovery session i have miss my online redolog files. why the datafiles are recovered.it's possible to recovered to online redo logs?
I've been using ASM for a few years now and have always installed a new system with 3 diskgroups
+DATA - for datafiles, control files, redo logs +FRA - for achive logs, flash recovery. RMAN backup
Those I guess are the standards, but I've always created an extra (very small) diskgroup, called +ONLINE where I keep multiplexed copies of the redo logs and control files.
My reasoning behind this is that if there are any issues with the +DATA diskgroup, the redo logs and control files can still be accessed.
In the olden days (all those 5 years ago!), on local storage, this was important, but is it still important now? With all the striping and mirroring going on (both at ASM and RAID level), am I just being overtly paranoid? Does this additional +ONLINE diskgroup actually hamper performance? (with dual write overheads that are not necessary)
I've only successfully duplicate a standby database.
from the alert log
ORA-00313: open failed for members of log group 1 of thread 1 ORA-00312: online log 1 thread 1: 'D:ORA102CTAREDO01.LOG' ORA-27041: unable to open file OSD-04002: unable to open file O/S-Error: (OS 2) The system cannot find the file specified.
[code].....
when I tried to add the online and standby redo log, it error out
SYS@CTA>select logdetail.member, loggroup.group#, loggroup.sequence#, loggroup.archived, loggroup.status lg_status, logdetail.status ld_detail, logdetail.type 2 from v$log loggroup join v$logfile logdetail 3 on loggroup.group# = logdetail.group#; MEMBER -------------------------------------------------------------------------------- GROUP# SEQUENCE# ARC LG_STATUS LD_DETA TYPE ---------- ---------- --- ---------------- ------- -------
[code].....
based on my understanding from [URL] ....
Quote:
As part of the duplicating operation, RMAN automates the following steps:
Creates a control file for the duplicate database
Restores the target datafiles to the duplicate database and performs incomplete recovery by using all available incremental backups and archived redo logs
Shuts down and starts the auxiliary instance (refer to "Task 4: Start the Auxiliary Instance" for issues relating to client-side versus server-side initialization parameter files)
Opens the duplicate database with the RESETLOGS option after incomplete recovery to create the online redo logs (except when running DUPLICATE ... FOR STANDBY, in which case RMAN does not open the database) when duplicating for standby database it does not create online redo logs. Duplicating a standby database does not creates online redo logs.
how should I add the online and standby redo logs. If I transfer the redo logs from primary to standby, it always encountered the the following error
Dump file d:ora102ctadumpcta_arc0_3624.trc Tue Sep 13 19:21:53 2011 ORACLE V10.2.0.4.0 - Production vsnsta=0 vsnsql=14 vsnxtr=3 Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - Production With the OLAP, Data Mining and Real Application Testing options Windows XP Version V5.1 Service Pack 2
I've got a legacy SAP system with oracle 8i on Tru64. No changes at all are made but for legal reasons we have to keep it up and running.
we currently do a full backup monthly by shutting down oracle and doing a backup of all the files to tape and that takes around 12 hours.
If I stop doing the full backup and I only backup the control file and the archived redo log files every month and I had to restore the full database years from now, would I be able to restore the database using the last full monthly backup and use the latest control file and archived redo log files?
The steps to move OMF files in ASM. I tried the following and was not successful.
RMAN> switch database to copy;
datafile 1 switched to datafile copy "+DATA01/pa01pod_im1l059p/datafile/system.357.809972853" datafile 2 switched to datafile copy "+DATA01/pa01pod_im1l059p/datafile/sysaux.363.809972837" datafile 3 switched to datafile copy "+DATA01/pa01pod_im1l059p/datafile/undotbs1.365.809972737" datafile 4 switched to datafile copy "+DATA01/pa01pod_im1l059p/datafile/users.361.809972859" datafile 5 switched to datafile copy "+DATA01/pa01pod_im1l059p/datafile/undotbs2.360.809972761" datafile 6 switched to datafile copy "+DATA01/pa01pod_im1l059p/datafile/undotbs3.359.809972787" datafile 7 switched to datafile copy "+DATA01/pa01pod_im1l059p/datafile/undotbs4.358.809972811"
RMAN> alter database open resetlogs;
RMAN-00571: =========================================================== RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS =============== RMAN-00571: =========================================================== RMAN-03002: failure of alter db command at 03/13/2013 16:30:05 ORA-01139: RESETLOGS option only valid after an incomplete database recovery
RMAN> alter database open;
so switch worked reset logs says can't use it there so I just try to open and it just hangs.
I have got backup pieces in ASM, I guess about more than 100 files. Now, I need to copy all of them from ASM to FileSystem, there are 2 methods still now:
1- Copy from ASM to FileSystem using cp command. 2- Copy from ASM to FileSystem using DBMS_FILE_TRANSFER.
But:
In the first method, when I copy one file, I took more than 1 minute, so the following script would take me more than 1 days (I guess so).
#!/bin/ksh # # This script copies files from FRA on ASM to local disk # ORACLE_SID=+ASM2 ASMLS=/vasgatedb/app/vsgbkp/asm_ls.txt ##{ASM files list}
[Code]...
The second method, DBMS_FILE_TRANSFER took me less than 1 second to copy one file completely.
sys@VSGDB> set timing on sys@VSGDB> exec dbms_file_transfer.COPY_FILE('asm_dir','level_0_vsgdb_9998_813844797.bkp','fs_dir','level_0_vsgdb_9998_813844797.bkp');
PL/SQL procedure successfully completed.
Elapsed: 00:00:00.38
Of course, I wish I used the second method as soon as possible, however, said I below, I've got about ~200 files, and I could not copy one by one file.
I have got oracle 11g release 1, I need recomendation, how can I delete safely content from the folder C:oraclediag dbmsinstancenameinstancenameincident?
ora-00257 archiver error. connect internal only until freed
when we tried to remove the unwanted arc files thro ASMCMD,we are getting below error:
ASMCMD> rm -ef 2011_04_05/ Unknown option: e usage: rm [-rf] <name1 name2 . . .> ASMCMD> rm -rf 2011_04_05/ ORA-15032: not all alterations performed ORA-15028: ASM file '+XCOM_BACKUP_DG/TXCOM/ARCHIVELOG/2011_04_05/thread_2_seq_27215.1143.747641143' not dropped; currently being accessed (DBD ERROR: OCIStmtExecute) ORA-15032: not all alterations performed ORA-15028: ASM file '+XCOM_BACKUP_DG/TXCOM/ARCHIVELOG/2011_04_05/thread_3_seq_21762.826.747641143' not dropped; currently being accessed (DBD ERROR: OCIStmtExecute) ORA-15032: not all alterations performed ORA-15177: cannot operate on system aliases (DBD ERROR: OCIStmtExecute)
