Transactions Vs Redo log

I want to know what happens when transaction activity level of a database decreases?
Is it increase , decrease or has no effect on the REDO log activities ?????
Is it increase or decrease the deadlock detection activity of the database??????
Regarding deadlocks I have a small doubt as well. Suppose there are 10 transactions, But suddenly all transactions get deadlocked. SO infact the transaction activity level goes down as all are stuck. But Shouldn't it INCREASE the deadlock detection activity here???????

damorgan wrote:
Redo logs sole purpose in Oracle is for recovery ... and they only contain committed transactions (from UNDO and data tablespaces).
In some cases online redo logs may contain uncommitted transactions as described in 11.2 Concepts Guide "Basic Instance Recovery Steps: Rolling Forward and Rolling Back" figure: http://download.oracle.com/docs/cd/E11882_01/server.112/e10713/startup.htm#BABBBFFG.
See also http://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:1670195800346464273

Similar Messages

  • How long redo logs keep the transactions?

    I learn Oracle and decide to do an experiment. There was a table in the test database. I deleted the file that contained this table via OS. And then I added transactions to this table.
    I did 'insert' several times, then 'commit', then 'alter system switch logfile' several times, 'alter system flush buffer_cache', 'alter system flush shared_pool' and nothing happened. I could add and take data from this table successfully. Alert log showed the error only when I shutdown the database.
    SQL> shutdown immediate
    ORA-01116: error in opening database file 13
    ORA-01110: data file 13: '/oracle/oradata/test5/POSTEMPTEST2.dbf'
    ORA-27041: unable to open file
    Linux Error: 2: No such file or directory
    Additional information: 3
    I understand that transactions are put in the redo logs at first, and then are transferred to the datafile on disk. I thought that command 'ALTER SYSTEM CHECKPOINT' writes transactions from redo logs to datafile on disk, but I was wrong. How long redo logs keep transactions? Is there the way to push data from redo logs to datafile?
    I use Oracle 10.2.0.1.0.

    i believe this time you will see the error message during your SQLsWRONG!probably you did not read the complete post of mine before saying WRONG. You tell me, if data file containing a table is deleted at OS level (in *nix), and then you try to insert data in this table and want to retrieve the data from the table (If data is not in db cache or cache has been flushed), from where data will come? Or if you want to insert some data into this table for which new extent are required to be allocated, where it will be allocated? Will your SQLs succeed or will return some error? Either SQL should return you data (which is not possible as data file is no there to fetch the data), or SQL should fail with some error message.
    I mimicked the situation on IBM AIX, following is the outcome.
    Enter user-name: system/salman
    Connected to:
    Oracle Database 11g Release 11.1.0.7.0 - 64bit Production
    SQL> create table test as select * from dba_tables;
    Table created.
    SQL> alter table test move tablespace users;
    Table altered.
    SQL> insert into test select * from dba_tables;
    2500 rows created.
    SQL> /
    2500 rows created.
    SQL> /
    2500 rows created.
    SQL> commit;
    Commit complete.Now i deleted the users01.dbf file at OS level and then execute following INSERT
    SQL> insert into test select * from test;
    insert into test select * from test
    ERROR at line 1:
    ORA-01565: error in identifying file '/oracle/oradata/test/users01.dbf'
    ORA-27037: unable to obtain file status
    IBM AIX RISC System/6000 Error: 2: No such file or directory
    Additional information: 3Salman

  • RAC Redo Log Internal

    Hi all
    I want ask some questions about redo log generation in RAC.
    1. Does Oracle confirms that each committed transaction, from begin_transaction to commit, redo and undo information resides in redo log of one node? Which means, would it possible that Oracle put begin transaction in redo log of node A, and put commit in redo log of another node B?

    Reup this thread :)
    Another questions:
    What about RAC broadcast performs? I mean is it true that when node A commits a transaction T, then it broadcast this information to all other nodes, would Oracle write this information about T to node B's online redo log? for example, in redo log of Node B contains a redo record including opcode=5.4 and T's transaction id and Node A's thread number.
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    So I wonder what Oracle does?
    Black Thought

  • Is There a Way to Run a Redo log for a Single Tablespace?

    I'm still fairly new to Oracle. I've been reading up on the architecture and I am getting the hang of it. Actually, I have 2 questions.
    1) My first question is..."Is there a way to run the redo log file...but to specify something so that it only applies to a single tablespace and it's related files?"
    So, in a situation where, for some reason, only a single dbf file has become corrupted, I only have to worry about replaying the log for those transactions that affect the tablespace associated with that file.
    2) Also, I would like to know if there is a query I can run from iSQLPlus that would allow me to view the datafiles that are associated with a tablespace.
    Thanks

    1) My first question is..."Is there a way to run the
    redo log file...but to specify something so that it
    only applies to a single tablespace and it's related
    files?"
    No You can't specify a redolog file to record the transaction entries for a particular tablespace.
    In cas if a file gets corrupted.you need to apply all the archivelogs since the last backup plus the redologs to bring back the DB to consistent state.
    >
    2) Also, I would like to know if there is a query I
    can run from iSQLPlus that would allow me to view the
    datafiles that are associated with a tablespace.Select file_name,tablespace_name from dba_data_files will give you the
    The above will give you the number of datafiles that a tablespace is made of.
    In your case you have created the tablespace iwth one datafile.
    Message was edited by:
    Maran.E

  • Can we use online redo log to recover lost datafile in NOARCHIVE mode?

    I am working on OCA exam and confued about these 2 sample questions. (similar questions with totally different answer)
    Please give me hint about the different between these 2 questions.
    ** If the database is in NOARCHIVELOG mode, and one of the datafile for tablespace USERS is lost, what kind of recovery is possible? (answer: B)
    A. All transactions except those in the USERS tablespace are recoverable up to the loss of the datafile.
    B. Recovery is possible only up to the point in time of the last full database backup.
    C. The USERS tablespace is recoverable from the online redo log file as long as none of the redo log files have been reused since the last backup.
    D. Tablespace point in time recovery is available as long as a full backup of the USERS tablespace exists.
    ** The database of your company is running in the NOARCHIVELOG mode. You perform a complete backup of the database every night. On Monday morning, you lose the USER1.dbf file belonging to the USERS tablespace. Your database has four redo log groups, and there have been two log switches since Sunday night's backup.
    Which is true (answer: B)
    A. The database cannot be recovered.
    B. The database can be recovered up to the last commit.
    C. The database can be recovered only up to the last completed backup.
    D. The database can be recovered by performing an incomplete recovery.
    E. The database can be recovered by restoring only the USER!.dbf datafile from the most recent backup.

    I think Gaurav is correct, you can recover to the last commit even in NOARCHIVELOG, as long as all the changes in the redo logs have not been overwritten. So answer should be B for question 2.
    Here is my test:
    SQL> select log_mode from v$database;
    LOG_MODE
    NOARCHIVELOG
    SQL> select tablespace_name, file_name from dba_data_files;
    TABLESPACE_NAME
    FILE_NAME
    USERS
    C:\ORACLE\PRODUCT\10.2.0\ORADATA\ORA101RC\USERS01.DBF
    SYSAUX
    C:\ORACLE\PRODUCT\10.2.0\ORADATA\ORA101RC\SYSAUX01.DBF
    UNDOTBS1
    C:\ORACLE\PRODUCT\10.2.0\ORADATA\ORA101RC\UNDOTBS01.DBF
    SYSTEM
    C:\ORACLE\PRODUCT\10.2.0\ORADATA\ORA101RC\SYSTEM01.DBF
    DATA
    C:\ORACLE\PRODUCT\10.2.0\ORADATA\ORA101RC\DATA01.DBF
    SQL> create table names
    2 ( name varchar(16))
    3 tablespace users;
    Table created.
    so this segment 'names' is created in the datafile users01.
    At this point I shut down and mount the DB, then:
    RMAN> backup database;
    channel ORA_DISK_1: backup set complete, elapsed time: 00:00:29
    Finished backup at 06-OCT-07
    SQL>alter database open
    SQL> insert into names values ('pippo');
    1 row created.
    SQL> commit;
    Commit complete.
    SQL>shutdown immediate;
    Database closed.
    Database dismounted.
    ORACLE instance shut down.
    At this point I delete datafile users01 and restart:
    SQL> startup
    ORACLE instance started.
    Total System Global Area 167772160 bytes
    Fixed Size 1247900 bytes
    Variable Size 67110244 bytes
    Database Buffers 96468992 bytes
    Redo Buffers 2945024 bytes
    Database mounted.
    ORA-01157: cannot identify/lock data file 4 - see DBWR trace file
    ORA-01110: data file 4: 'C:\ORACLE\PRODUCT\10.2.0\ORADATA\ORA101RC\USERS01.DBF'
    restoring the backup taken before inserting the value 'pippo' in table names:
    RMAN> restore database;
    Starting restore at 06-OCT-07
    using channel ORA_DISK_1
    channel ORA_DISK_1: starting datafile backupset restore
    channel ORA_DISK_1: specifying datafile(s) to restore from backup set
    restoring datafile 00001 to C:\ORACLE\PRODUCT\10.2.0\ORADATA\ORA101RC\SYSTEM01.D
    BF
    restoring datafile 00002 to C:\ORACLE\PRODUCT\10.2.0\ORADATA\ORA101RC\UNDOTBS01.
    DBF
    restoring datafile 00003 to C:\ORACLE\PRODUCT\10.2.0\ORADATA\ORA101RC\SYSAUX01.D
    BF
    restoring datafile 00004 to C:\ORACLE\PRODUCT\10.2.0\ORADATA\ORA101RC\USERS01.DB
    F
    restoring datafile 00005 to C:\ORACLE\PRODUCT\10.2.0\ORADATA\ORA101RC\DATA01.DBF
    channel ORA_DISK_1: reading from backup piece C:\ORACLE\PRODUCT\10.2.0\DB_1\DATA
    BASE\0AITR52K_1_1
    channel ORA_DISK_1: restored backup piece 1
    piece handle=C:\ORACLE\PRODUCT\10.2.0\DB_1\DATABASE\0AITR52K_1_1 tag=TAG20071006
    T181337
    channel ORA_DISK_1: restore complete, elapsed time: 00:02:07
    Finished restore at 06-OCT-07
    RMAN> recover database;
    Starting recover at 06-OCT-07
    using channel ORA_DISK_1
    starting media recovery
    media recovery complete, elapsed time: 00:00:05
    Finished recover at 06-OCT-07
    SQL> alter database open;
    Database altered.
    SQL> select * from names;
    NAME
    pippo
    SQL>
    enrico

  • Hoping for a quick response : EXP and Archived REDO log files

    I apologize in advance if this question has been asked and answered 100 times. I admit I didn't search, I don't have time. I'm leaving on vacation tomorrow, and I need to know if I'm correct about something to do with backup / restore.
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    exp system/xpwdxx@db full=y file=D:\Orant\admin\db\EXP\db_full.dmp log=D:\Orant\admin\db\EXP\db_full.txt direct=y compress=y
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    Te database is running in autoarchive mode. The problem is, the archived redo files filled the drive they were being stored on, and it is the drive the database is on. I used OS commands to move 136G of archived redo logs onto other storage media to free the drive.
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    Hoping for a quick response
    Best Regards, and thanks in advance
    Bruce Davis

    Bruce Davis wrote:
    Amardeep Sidhu
    Thank you for your quick reply. I am reading in the other responses that since I am using EXP without consistent=y, I might not even have a backup. The application vendor said that with this dmp file they can restore us to the most recent backup. I don't really care for this strategy as it is untested. I asked them to verify that they could restore us and they said they tested the dmp file and it was OK.
    Thank you for taking the time to reply.
    Best Regards
    BruceThe dump file is probably ok in the sense it is not corrupted and can be used in an imp operation. That doesn't mean the data in it is transactionally consistent. And to use it at all, you have to have a database up and running. If the database is physically corrupted, you'll have to rebuild a new database from scratch before you can even think about using your dmp file.
    Vendors never understand databases. I once had a vendor tell me that Oracle's performance would be intolerable if there were more than 5 concurrent connections. Well, maybe in HIS product ..... Discussions terminated quickly after he made that statement.

  • Dataguard lost both Primary redo log and standby redo log files

    Hi,
    I am new to data guard, i came acorss a scenario where we loose both primary redo log file and standby redo log files.
    Can someone please help me understand how to recover from this situation.
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    >loose both primary redo log file and standby redo log files
    We have to be very clear.
    There are (set A) online redo log files  and (set B) standby redo log files at (location 1) Primary and (location 2) Standby.
    The standby redo log files, depending on the configuration, aren't strictly mandatory.  The standby can be applying redo without online redo log files present as well, depending on how it was setup.
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  • Fundamental questions on redo logs and rollbacks

    Hi all,
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    Suppose that we have updated few records in a table. We know that the blocks to be updated will be fetched into buffer cache, they will be updated with new value and commited eventually. The questions I have are ,
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    2) What exactly goes to rollback segment? is it copy of block before change (for update) and just the rowid for inserted row and the copy of block for a deleted row ?
    3) Whatever we do, is it the whole block that goes to redo or rollback ? Means if there are 10 rows in the block and we update one of them, still whole block goes to redo or rollback ?
    4) If we rollback, what goes where ? Is there anything that goes to redo if we rollback ?
    Please explain.
    Thanks.

    Redo stores changes made in the database, and undo/rollback stores the reverse of those changes. Data blocks may be changed prior to a commit, and recorded in both locations.
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    Undo/rollback can also be used simply to roll back a transaction in an active instance. Redo is only used during instance recovery.
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  • Oracle 10g R2 Database Redo Log Files

    I had 3 redo log files, each of size 50 MB. i added 3 more redo log files, each of size 250 MB.
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    to make all archive redo log files generation of equal size what should i do?
    Please guide

    Waheed,
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    to make all archive redo log files generation of equal size what should i do?
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    Aman....

  • Redo log files in case of NOARCHIVELOG Mode.

    Question is related with the oracle architure..
    database requires a minimum of two redo log files to guarantee that one is always available for writing while the other is being archived, this sounds perfect when DB is running in ARCHIVELOG mode but at the same time it also forces database to have 2 redo log files even when the DB is running in NOARCHIVELOG mode?
    Any particular reason..
    I would look for reasons not answers on what redo log is and what information it holds etc..

    pgoel wrote:
    If you had only one file all further changes would have to stop until all changed data blocks had been written to disc. By insisting on a minimum of two log files Oracle can allow the log writer to fill the second log file as the database writer writes out the dirty blocks covered by changes desrcibed in the first log file.What about having a big size redo log file instead of two? Checkppoint being initiated when the redo log file is half filled
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    HTH
    Aman....

  • DB Cache Full or Redo Log Full?

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    The error is "ORA-00379: no free buffers available in buffer pool DEFAULT for block size 8K"
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    I am referring to the same problem outlined in an earlier thread.
    Thanks

    Is there any way that Oracle can write to datafiles
    in the middle of a transaction?
    r.- Oracle writes to the datafiles only commited transactions according to some elements
    Iam reading, processing and writing very large sized
    lobs which gives error that "no free buffers
    available in buffer pool".
    r.- You have to increase the size of the buffer Pool
    When in lobs, a lob is not written until the whole
    tranaction finishes - but in my case the lob size is
    large than the size of the data buffer cache.
    The error is "ORA-00379: no free buffers available in
    buffer pool DEFAULT for block size 8K"
    Exact question I would like to know now is that which
    buffer is full; data_buffer_cache or the redo log
    buffer?
    data_buffer_cache. In what version you are ?
    If data_buffer cache, then is there a mechanism which
    allows to write data to dtafiles in the middle of a
    transaction as i have to do processing with lobs -
    which are 3 to 4 times the size of the db cache
    size.
    r.- Oracle does not write to the datafiles in that way
    I am referring to the same problem outlined in an
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    Thanks Joel Pérez
    http://www.oracle.com/technology/experts

  • Bottleneck when switching the redo log files.

    Hello All,
    I am using Oracle 11.2.0.3.
    The application team reported that they are facing slowness at certain time.
    I monitored the database and I found that at some switching of the redo log files (not always) I am facing a slowness at the application level.
    I have 2 threads since my database is RAC, each thread have 3 redo log groups multiplexed to the FRA, with size 300 MB each.
    Is there any way to optimize the switch of redo log files? knowing that my database is running in ARCHIVELOG mode.
    Regards,

    Hello Nikolay,
    Thanks for your input I am sharing with you the below information. I have 2 instances so I will provide the info from each instance
    Instance 1:
    Load Profile              Per Second    Per Transaction   Per Exec   Per Call
    ~~~~~~~~~~~~         ---------------    --------------- ---------- ----------
          DB Time(s):                4.9                0.0       0.00       0.00
           DB CPU(s):                1.1                0.0       0.00       0.00
           Redo size:        3,014,876.2            3,660.4
       Logical reads:           32,619.3               39.6
       Block changes:            7,969.0                9.7
      Physical reads:                0.2                0.0
    Physical writes:              164.0                0.2
          User calls:            7,955.4                9.7
              Parses:              288.9                0.4
         Hard parses:               96.0                0.1
    W/A MB processed:                0.2                0.0
              Logons:                0.9                0.0
            Executes:            2,909.4                3.5
           Rollbacks:                0.0                0.0            
    Instance 2:
    Load Profile              Per Second    Per Transaction   Per Exec   Per Call
    ~~~~~~~~~~~~         ---------------    --------------- ---------- ----------
          DB Time(s):                5.5                0.0       0.00       0.00
           DB CPU(s):                1.4                0.0       0.00       0.00
           Redo size:        3,527,737.9            3,705.7
       Logical reads:           29,916.5               31.4
       Block changes:            8,893.7                9.3
      Physical reads:                0.2                0.0
    Physical writes:              194.0                0.2
          User calls:            7,742.8                8.1
              Parses:              262.7                0.3
         Hard parses:               99.5                0.1
    W/A MB processed:                0.4                0.0
              Logons:                1.0                0.0
            Executes:            2,822.5                3.0
           Rollbacks:                0.0                0.0
        Transactions:              952.0
    Instance 1:
    Top 5 Timed Foreground Events
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
                                                               Avg
                                                              wait   % DB
    Event                                 Waits     Time(s)   (ms)   time Wait Class
    DB CPU                                            1,043          21.5
    log file sync                       815,334         915      1   18.9 Commit
    gc buffer busy acquire              323,759         600      2   12.4 Cluster
    gc current block busy               215,132         585      3   12.1 Cluster
    enq: TX - row lock contention        23,284         264     11    5.5 Applicatio
    Instance 2:
    Top 5 Timed Foreground Events
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
                                                               Avg
                                                              wait   % DB
    Event                                 Waits     Time(s)   (ms)   time Wait Class
    DB CPU                                            1,340          24.9
    log file sync                       942,962       1,125      1   20.9 Commit
    gc buffer busy acquire              377,812         594      2   11.0 Cluster
    gc current block busy               211,270         488      2    9.1 Cluster
    enq: TX - row lock contention        30,094         299     10    5.5 Applicatio
    Instance 1:
    Operating System Statistics        Snaps: 1016-1017
    -> *TIME statistic values are diffed.
       All others display actual values.  End Value is displayed if different
    -> ordered by statistic type (CPU Use, Virtual Memory, Hardware Config), Name
    Statistic                                  Value        End Value
    AVG_BUSY_TIME                             17,451
    AVG_IDLE_TIME                             81,268
    AVG_IOWAIT_TIME                                1
    AVG_SYS_TIME                               6,854
    AVG_USER_TIME                             10,548
    BUSY_TIME                                420,031
    IDLE_TIME                              1,951,741
    IOWAIT_TIME                                  288
    SYS_TIME                                 165,709
    USER_TIME                                254,322
    LOAD                                           3                6
    OS_CPU_WAIT_TIME                         523,000
    RSRC_MGR_CPU_WAIT_TIME                         0
    VM_IN_BYTES                              311,280
    VM_OUT_BYTES                          75,862,008
    PHYSICAL_MEMORY_BYTES             62,813,896,704
    NUM_CPUS                                      24
    NUM_CPU_CORES                                  6
    NUM_LCPUS                                     24
    NUM_VCPUS                                      6
    GLOBAL_RECEIVE_SIZE_MAX                4,194,304
    GLOBAL_SEND_SIZE_MAX                   4,194,304
    TCP_RECEIVE_SIZE_DEFAULT                  16,384
    TCP_RECEIVE_SIZE_MAX      9.2233720368547758E+18
    TCP_RECEIVE_SIZE_MIN                       4,096
    TCP_SEND_SIZE_DEFAULT                     16,384
    TCP_SEND_SIZE_MAX         9.2233720368547758E+18
    TCP_SEND_SIZE_MIN                          4,096
    Operating System Statistics - Detail  Snaps: 1016-101
    Snap Time           Load    %busy    %user     %sys    %idle  %iowait
    22-Aug 11:33:55      2.7      N/A      N/A      N/A      N/A      N/A
    22-Aug 11:50:23      6.2     17.7     10.7      7.0     82.3      0.0
    Instance 2:
    Operating System Statistics         Snaps: 1016-1017
    -> *TIME statistic values are diffed.
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    Statistic                                  Value        End Value
    AVG_BUSY_TIME                             11,823
    AVG_IDLE_TIME                             86,923
    AVG_IOWAIT_TIME                                0
    AVG_SYS_TIME                               4,791
    AVG_USER_TIME                              6,991
    BUSY_TIME                                475,210
    IDLE_TIME                              3,479,382
    IOWAIT_TIME                                  410
    SYS_TIME                                 193,602
    USER_TIME                                281,608
    LOAD                                           3                6
    OS_CPU_WAIT_TIME                         615,400
    RSRC_MGR_CPU_WAIT_TIME                         0
    VM_IN_BYTES                               16,360
    VM_OUT_BYTES                          72,699,920
    PHYSICAL_MEMORY_BYTES             62,813,896,704
    NUM_CPUS                                      40
    NUM_CPU_CORES                                 10
    NUM_LCPUS                                     40
    NUM_VCPUS                                     10
    GLOBAL_RECEIVE_SIZE_MAX                4,194,304
    GLOBAL_SEND_SIZE_MAX                   4,194,304
    TCP_RECEIVE_SIZE_DEFAULT                  16,384
    TCP_RECEIVE_SIZE_MAX      9.2233720368547758E+18
    TCP_RECEIVE_SIZE_MIN                       4,096
    TCP_SEND_SIZE_DEFAULT                     16,384
    TCP_SEND_SIZE_MAX         9.2233720368547758E+18
    TCP_SEND_SIZE_MIN                          4,096
    Operating System Statistics - Detail Snaps: 1016-101
    Snap Time           Load    %busy    %user     %sys    %idle  %iowait
    22-Aug 11:33:55      2.6      N/A      N/A      N/A      N/A      N/A
    22-Aug 11:50:23      5.6     12.0      7.1      4.9     88.0      0.0
              -------------------------------------------------------------

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