I'm an Oracle novice and from what I've read so far, it seems that you should be able to do rollbacks and data recovery using the redo logs. I'm having a difficulty understanding the need for the undo tablespace.
View 2 Repliesit seems that you should be able to do rollbacks and data recovery using the redo logs. I'm having a difficulty understanding the need for the undo tablespace.
View 3 Replies View Relatedregarding sizing undo tablespace and undo_retention parameter.we have to implement the database in production system with 40 users but how much space should be allocated to undo tablespace is there any propotions related to virtual memory and the
parameter.i have gone thru oracle doc's and some related sites.its an ERP aplications that contains 20 modules .I am an new one to this dba level
I am using Oracle 10.2.0.3. Since yesterday i am seeing a session with sid 1160 using undo tablespace but not able to find how much it is using .I need to know which session and from which module and how much is the Undo being used by those sessions. I have tried searching but all the queries provide me with some different results each time.
Also i need the same information for REDO being generated .
I'm using Oracle 10gR2 (10.2.0.4.0) 64 bits.
I got many times oracle ORA-00494 error and the database went down but since 29th of july the database have not been killed.
The error message is below :
ORA-00494: mise en file d'attente [CF] d�tenue pendant trop longtemps ( (more than 900 seconds)) par inst 1, osid 176484
ORA-00028: votre session a �t� ferm�e
My database is used for datawarehouse of many terabytes.
Initially the redo log size was 500Mbytes and I've set it to 3Gbytes. The maximum log switch is after 5 minutes. I want log to be switched every 20 minutes or every 30 minutes.
To obtain the size of redo logs I've executed this query :
SQL> select OPTIMAL_LOGFILE_SIZE from v$instance_recovery;
OPTIMAL_LOGFILE_SIZE
--------------------
54763
53,5 Gbytes is it not very big as redo log size? What's the maximum size of redo log? To set very big redo log size what are the requirements? Which precautions should I take before? What are the risks? Are any other ways to change the log switch frequency?
is it Any way I can put the size of my redo log (During Install Oracle DB 11.1.0.7 )
I mean during installtion .??? becouse its by default 50 MB I need to be 200MB
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?
Version: 11.2.0.3Platform : Solaris 10
One of the Hitachi support guy has suggested to create a separate disk group for Online redo logs. His rationale was that ORLs was write only files and it would be better to put in a separate disk group.
This morning when I checked my archive logs, I suprised that the redo files are generating after every 3 min and each of file size is 50M, which is the actual size of both log members. I m using RAC database with DR server.Usally the total redo logs quantity for one day is 4 to 5. but since 10 pm of yesterday to 7 am today, the quantity of log files are 109, each of 50 M .
View 2 Replies View RelatedI'm running Oracle 9i on AIX 5.2. I'm not using a recovery catalog, nor am I using media management software. I perform a full, online rman backup of the database and archived redo logs daily to disk, then use operating system commands to copy the backup to tape. There is only space on disk for two days' backups, so I need to have a retention policy of "redundancy = 1", and run a "delete obsolete" prior to the backup. The problem is that I don't want to subject the archived redo logs to this retention policy.
I have two physical standby databases connected by WAN to the primary site, and I might need archived redo logs that are a few days (or more) old in the event of a prolonged WAN outage. I've read about the "keep forever" option, but apparently it isn't available without using a recovery catalog. Is there any way to spare the archived redo logs from my retention policy?
Note: I want to "protect" the actual archived redo logs from the retention policy, not the backups of the archived redo logs.
While Configuring Data Guard for ORacle 10g (10.2.0.4) 64 bits on Windows 2007 Server 64 bits.I got few questions
1. What is the Default mode of Standby Database?
2. Should we Always Start Physical Standby Database to Recover Missing Redo Archive Log?
SQL> startup mount;
ORACLE instance started.
Total System Global Area 591396864 bytes
Fixed Size 2067496 bytes
Variable Size 163578840 bytes
Database Buffers 419430400 bytes
Redo Buffers 6320128 bytes
Database mounted.
SQL> alter database recover managed standby database disconnect from session;
Database altered.
3. When there are missing Redo Log Archives e.g.
----On Standby Database--------
SQL> SELECT RESETLOGS_ID,SEQUENCE#,STATUS,ARCHIVED FROM V$ARCHIVED_LOG
2 ORDER BY RESETLOGS_ID,SEQUENCE#;
RESETLOGS_ID SEQUENCE# S ARC
------------ ---------- - ---
812980008 15 A YES
812980008 16 A YES
812980008 17 A YES
812980008 18 A YES
[code]....
65 rows selected. Log 8, 9, 10, 11, 12, 13, 14, 15 are missing.
How to Apply / Recover These Logs on Standby Database?
URL....I'm practicing for the OCP test and one of the questions is that there is a backup from yesterday and the last archived logs are from the day before yesterday not mentioned if it's cold or hot backup.
If its a cold backup - cant we recover it? is it a must to have the archived redo logs also when recovering a cold backup? That sounds not logical since those logs are made only for a hot backup. URL.....
How do we check current redologs are sized properly.if there is any script to check that.
View 7 Replies View RelatedI'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)
At a time my 20 GB undo tablespace was full. So i increased the tablespace size upto 48 GB. Then i saw 45 GB was used. Then i changed undo_retention=60. After that am seeing that 48 GB is full.
1) why it's happened?
2) Here what is the effect of undo_retention=60
3) How to resolve?.
Can an undo tablespace be too large and actually hurt performance? I have seen a system with a dedicated 1 TB drive for undo tablespace (no guarantee) with an undo_retention of 7 days. Would this hurt performance? What about setting an undo_retention of 24 hours with no guarantee? The only mention I could find online said that it would not hurt performance but I wanted to double check. You would think that Oracle does not care if it deletes the undo at 15 minutes or if it deletes the undo at a later date such as 7 days later and the performance should stay the same.
View 3 Replies View RelatedI am trying to drop 90 columns from a big partitioned table. I was trying a physical drop first and since it is taking longer time I decided make the columns unused state and drop them. However I was able to set them to unused state.
Now I am trying to drop those unused columns from the table, it is running since 22hours Apporox. I am keep increasing the undo tablespace to retain the undo data.
I also have decreased the undo_retention to 300 from 900.
My question is there any better way to drop these columns. And is there any way to flush out the data from undo.
S:Solaris
DB:10g
I am simulating a recovery of drop undo tablespace. for the same I have done the following things:
1. Dropped the only undo datafile from the os level while the database was open.
2. Then I created a table and inserted and updated some values in it and I was also allowed to commit.
When I am updating the rows of the table,the before images must have been written to UNDO but in my case there is no UNDO datafile.
i Cannot drop old undo tablespace. While dropping the old undo tablespace we get an error
ERROR at line 1: ORA-01548: active rollback segment '_SYSSMU77$' found, terminate dropping tablespace
SQL> select tablespace_name, status, segment_name from dba_rollback_segs where status != 'OFFLINE';
TABLESPACE_NAME STATUS SEGMENT_NAME
------------------------------ ---------------- ------------------------------
SYSTEM ONLINE SYSTEM
APPS_UNDO NEEDS RECOVERY _SYSSMU77$
When i takeind export i got error like this..
ORA-39125: Worker unexpected fatal error in KUPW$WORKER.GET_TABLE_DATA_OBJECTS while calling DBMS_METADATA.FETCH_XML_CLOB [TABLE_DATA:"POS"."TBK_POS_FACT":"KROATL200404"]
ORA-01555: snapshot too old: rollback segment number 1 with name "_SYSSMU1$" too small"
from this can we increase the undo_retention value or undo tablespace size?
As the undo segments are used in round robin fashion, Is it possible that with varying load (concurrent users, size and number of transactions), the size of Undo tablespace on a particular day is less than the Undo tablespace size few days back, by any chance?
As a basic understanding I know that Undo is preserved for read consistency and transaction, instance recovery So if there are lot of transaction on a database on 05 Feb and before that, but there aren't any transactions on 6,7,8,9, then on 10th Feb can we see the Undo tablespace size is less than that of 05 Feb?
In the following case when data belonging to table is not required for any queries, transactions, even then the undo size is not restored upon dropping the table.
As such for large operations and batch processes shall we keep undo tablespace with files as 'Autoextend' with 'Maxsize' as 'Unlimited'?
SQL> select b.tablespace_name, Total_Kbytes_Available/1024 Tot_Mbytes_Available,
Kbytes_alloc/1024 Mbytes_allocated, kbytes_free/1024 Mbytes_Free_from_allocated,
((Kbytes_alloc - kbytes_free)*100/ Total_Kbytes_Available) Pctused
2 from ( select sum(bytes)/1024 Kbytes_free,
3 tablespace_name
4 from sys.dba_free_space
[code]....
why total size for undotbs1 is different from the acutal data file size in Operating system.
select tablespace_name, sum(bytes/1024/1024) from dba_data_files
where tablespace_name like 'UNDO%'
group by tablespace_name;
tablespacename total size
UNDOTBS1 2000
UNDOTBS2 7284
[code]....
rdbms 11gr2 undo tablespace is not fixed size. and the undo guarantee is not set.should we set undo_retention to
select max(tuned_undoretention) from v$undostat ; to avoid 1555 error?
you have an undo tablespace which has autoextend on feature.after a timegap your undo tablespace presently is 100GB
here as a DBA what you will do?
When I am importing, I get these errors
IMP-00019: row rejected due to ORACLE error 1
IMP-00003: ORACLE error 1 encountered
ORA-00001: unique constraint (XXXXXXXXXXXXXXXX) violated
Column 1 2
Column 2 OFFLINE
[code]....
I added a datafile in undo tablespace (its an ASM database). I doubt that since I added the datafile to undo tablespace, I am getting this error.
Operating System - WindowXP
oracle version 10.2.0.1
I was learning some recovery part in my home laptop. Database is in Archivelog, flashback mode. All of sudden, i deleted it from OS level with out taking backup of it.
When i tried to open database, it failed to start. Database is in mount mode.while trying to open, it gives message -
ORA-01157: cannot identify/lock data file 1 - see DBWR trace file
ORA-01110: data file 1: 'F:ORACLEPRODUCT10.2.0ORADATADBSYSTEM01.DBF'
I tried to create on file named "UNDOTBS01.DBF" but oracle is not recognizing it.
we have a situation where both undo tablespaces were almost filled i.e UNDOTBS1 99% and UNDOTBS2 100% filled so i add data files to it and then i found a lot of blocking session and was just killing them through EM then i stop my front end listener and also down the service, now i don't have any blocking session but on EM a big WAIT is coming. alert log shows nothing serious, it was showing deadlock but now it is over as well.
View 8 Replies View RelatedI have a serious doubt in oracle architecture functionality, when a user issues a update statement the data blocks are carried to db buffer cache and where does the changes to the data blocks are made???? Does a copy of the data block is kept in db buffer cache and the changes are made to the block in buffer cache?? or the a copy of the data block is kept in undo tablespace and changes are made to the blocks in the undo tablespace???
In simple the changes to the data blocks are made at db buffer cache or undo tablespace?
i'm facing a problem while i'm inserting millions of record from table to table that undo tablespace reach 100% full and execution aborted. , how can free the undo tablespace ??? many of extendes are offline. will it flush automatically ??? or what i should do
View 4 Replies View RelatedCan we find out no of undo segments in undo Table space ? If so , how to find? what's their max limit ?
View 9 Replies View Related