Logging buffer - what size?

Similar Questions

• Question about the size of the redo log buffer

  Hello
  
  I am a student in Oracle and the book I use says that having a bigger than the buffer log by default, the size is a bad idea.
  
  It sets out the reasons for this are:
  
  >
  The problem is that when a statement COMMIT is issued, part of the batch validation means to write the contents of the buffer log for redo log to disk files. This entry occurs in real time, and if it is in progress, the session that issued the VALIDATION will be suspended.
  >
  
  I understand that if the redo log buffer is too large, memory is lost and in some cases could result in disk i/o.
  
  What I'm not clear on is, the book makes it sound as if a log buffer would cause additional or IO work. I would have thought that the amount of work or IO would be substantially the same (if not identical) because writing the buffer log for redo log files is based on the postings show and not the size of the buffer itself (or its satiety).
  
  Description of the book is misleading, or did I miss something important to have a larger than necessary log buffer?
  
  Thank you for your help,
  
  John.
  
  Published by: 440bx - 11 GR 2 on August 1st, 2010 09:05 - edited for formatting of the citation

  A commit evacuates everything that in the buffer redolog for redo log files.
  A redo log buffer contains the modified data.
  But this is not just commit who empty the redolog buffer to restore the log files.
  LGWR active every time that:
  (1) a validation occurs
  (2) when the redo log is 1/3 full
  (3) every 3 seconds
  It is not always necessary that this redolog file will contain validated data.
  If there is no commit after 3 seconds, redologfile would be bound to contain uncommitted data.

  Best,
  Wissem

• The log buffer size

  Hello
  Could someone please confirm that the following query returns log buffer size is correct?
  

  select 
     a.ksppinm name, 
     b.ksppstvl value, 
     a.ksppdesc description
  from
     x$ksppi a, 
     x$ksppcv b
  where 
     a.indx = b.indx
  and 
     a.ksppinm = '_ksmg_granule_size';

  The reason I ask is this log_buffer parameter in v$ parameter in my database has a value of 7024640, while the query return 4194304.
  
  Thank you.

  Hello..

  The '_ksmg_granule_size' "shows the size of granule not size log_buffer. If the total size of the SGA is equal to or less than 1 GB, then granule size is 4 MB. For greater than 1 GB EAG, granule size is 16 MB.

  What is the size of the SGA of your database.

  For my database SGA > 1 GB the output of the query is 16 MB
  {code}
  21:41:47 TEST > value col to a25
  21:41:56 TEST > col DESCRIPTION for a30
  21:42:05 TEST >
  21:42:05 TEST >
  21:42:05 TEST >
  21:42:05 TEST > select
  21:42:08 2 a.ksppinm name,
  21:42:12 3 b.ksppstvl value,
  21:42:12 4 a.ksppdesc description
  21:42:12 5 of
  21:42:12 6 x$ ksppi has.
  21:42:12 x $7 ksppcv b
  21:42:12 8 where
  21:42:12 a.indx 9 = b.indx
  21:42:12 10 and
  21:42:12 11 a.ksppinm = '_ksmg_granule_size ';

  NAME VALUE DESCRIPTION
  -------------------- ------------------------- ------------------------------
  granule _ksmg_granule_size 16777216 bytes in size
  {code}

  HTH
  Anand

• How do to the size of the log buffer reduce with huge Pages Linux

  Data sheet:

  Database: Oracle Standard Edition 11.2.0.4

  OS: Oracle Linux 6.5

  Processor: AMD Opteron

  Sockets: 2

  Carrots / power outlet: 16

  MEM: 252 GB

  Current SGA: GB 122 automatic shared memory (EAMA) management

  Special configuration: Linux huge Pages for 190 GB of memory with the page size of 2 MB.

  Special configuration II: The use of the LUKS encryption to all drives.

  Question:

  1. How can I reduce the size of the log buffer? Currently, it appears that 208 MB. I tried to use log_buffer, and it does not change a thing. I checked the granule size is 256 MB with the current size of the SGA.

  Reason to reduce:

  With the largest size of log buffer the file parallel write newspaper and the synchronization log file is averaged over 45 ms most of the time because she has dumped a lot of stuff at the same time.

  Post edited by: CsharpBsharp

  You have 32 processors and 252 GB of memory, so 168 private discussions, so 45 MB as the public threads size is not excessive.  My example came from a machine running Oracle 32-bit (as indicated by the size of 64 KB of threads private relative to the size of 128 KB of your son) private with (I think) 4 GB of RAM and 2 CPUs - so a much smaller scale.

  Your instance was almost inactive in the meantime so I'd probably look outside the Oracle - but verification of the OS Stats may be informative (is something outside the Oracle using a lot of CPU) and I would like to ask you a few questions about encrypted filesystems (LUKS).  It is always possible that there is an accounting error - I remember a version of Oracle who report sometimes in milliseconds while claiming to centisecondes - so I'll try to find a way to validate the log file parallel write time.

  Check the forum for any stats activity all over again (there are many in your version)

  Check the histogram to wait for additional log file writes event (and journal of file synchronization - the lack of EPA top 5 looks odd given the appearance of the LFPW and and the number of transactions and redo generated.)

  Check the log file to track writer for reports of slow writes

  Try to create a controlled test that might show whether or not write reported time is to trust (if you can safely repeat the same operation with extended follow-up enabled for the author of newspaper which would be a very good test of 30 minutes).

  My first impression (which would of course be carefully check) is that the numbers should not be approved.

  Concerning

  Jonathan Lewis

• Can make the size of the log buffer be changed or is managed internally by oracle

  Can again change the log buffer size? or is managed internally by oracle in the SGA? We are on oracle 10.2.0.3.
  
  The reason why I asked the question was that our construction team do estimates for data/memory sizing properly... so we wanted to know if it can be changed or not?

  Hi S2k!

  The SGA Memorystructure is handled automatically by Oracle, if the SGA_TARGET initializationparameter is set. But nothing less you are able to configure the size of a memorystructure by yourself. Here is a good article on the optimization of the log buffer.

  [http://www.dba-oracle.com/t_log_buffer_optimal_size.htm]

  I hope this will help you along.

  Yours sincerely

  Florian W.

• Redo Log Buffer 32.8 M, looks great?

  I just took on a database (mainly used for OLTP on 11 GR 1 matter) and I'm looking at the level of the log_buffer parameter on 34412032 (32.8 M). Not sure why it is so high.
  

  select 
      NAME, 
      VALUE
  from 
      SYS.V_$SYSSTAT
  where 
      NAME in ('redo buffer allocation retries', 'redo log space wait time');
  
  redo buffer allocation retries     185
  redo log space wait time          5180

  (database was for 7.5 days)
  
  Any advice on that? I normally keep trying to stay below 3 m and have not really seen it above 10 M.

  Sky13 wrote:
  I just took on a database (mainly used for OLTP on 11 GR 1 matter) and I'm looking at the level of the log_buffer parameter on 34412032 (32.8 M). Not sure why it is so high.

  11g, you should not set the log_buffer - only Oracle default set.

  The value is derived relative to the setting for the number of CPUS and the transaction parameter, which can be derived from sessions that can be derived processes. In addition, Oracle will allocate at least one granule (which can be 4, 8 MB, 16 MB, 64 MB, or 256 MB depending on the size of the SGA, then you are not likely to save memory by reducing the size of the log buffer.

  Here is a link to a discussion that shows you how to find out what is really behind this figure.
  Re: Archived redo log size more than online redo logs

  Concerning
  Jonathan Lewis
  http://jonathanlewis.WordPress.com
  Author: core Oracle

• Download photoshop cc and it stuck at 2% - DSL download at 6 Mbps - What size is this program and why it is frozen at 2%

  Download photoshop cc and it stuck at 2% - DSL download at 6 Mbps - What size is this program and why it is frozen at 2%

  Jimk88 I recommend you review the download logs to determine the exact error.  You can find details on how to locate the logs from download to download the Cloud Creative applications error - http://helpx.adobe.com/creative-cloud/kb/error-downloading-cc-apps.html.

• REDO LOG BUFFER DOUBT

  Hi EXPERTS,
  
  IM on 11 G R2, RHEL 5 my question that when the data changes in the database buffer cache how immediately it is copied in the redo log buffer. I mean what process the copy. I read it in the oracle documentation only when waiting for event [log file command (private stream flush incomplete)] LGWR waits DBWR again complete flushing of buffers IMU in the recovery log buffer. Completion of DBWR LGWR can then finish writing the log in process and then move the log files.
  

• relationship between redo log buffer, journal of redo and undo tablespace files

  What is the relationship between the redo log buffer, redo log files and undo tablespace?
  
  what I understand is
  
  redo log buffer is the logical area where all the news of recovery were stored until they are transferred by LGWR bank roll forward log online... but y at - it report any with the undo tablespace with these two?
  
  Please correct me if I'm wrong
  
  Thanks in advance

  redo log buffer is the logical area where all the news of recovery were stored until they are transferred by LGWR bank roll forward log online... but y at - it report any with cancellations

  tablespace with these two?

  There is a link between files redo log and buffer, but the undo tablespace is something else entirely.

  spend it here with this links

  REDO LOG FILES
  http://www.DBA-Oracle.com/concepts/redo_log_files.htm

  BUFFER REDOLOG
  http://www.DBA-Oracle.com/concepts/redo_log_buffer_concepts.htm

  UNDO TABLESPACE
  Undo tablespace to cancel files to undo or roll back uncommitted changes pray the database.

  Hope you understood.

• LOG BUFFER

  Hi experts,
  
  My question is: = whence the changes in the log buffer? Does cache buffers UGA or database. If UGA then what part of the UGA. And copy that into the log buffer. This is the server process.

  800978 wrote:
  Hi experts,

  My question is: = whence the changes in the log buffer? Does cache buffers UGA or database. If UGA then what part of the UGA. And copy that into the log buffer. This is the server process.

  Well, you ask too many questions that can be answered in the documentation. Please note that the following messages which must mention your version of db (4 digits) regardless of how irrelevant you think that maybe.

  For your question, this post of mine,.
  http://blog.aristadba.com/?p=17

  Read the article to Redo buffers and buffers Sales.

  HTH
  Aman...

• Redo Log Buffer - Online redo - archived journal - LGWR

  Hello
  
  It is specified in this document that redo entries is set to all changes (LMD), the database Redo Log Buffer (my question is when does? after validation?).
  
  And, in this connection, they say engaged and committed changes in the section again. But when you scroll down to the section Commit on the same link, after a commit log writer process (LGWR) will write journal entries of the SGA (log buffer) forward in the line redo log file.
  
  I wonder how? When I tested it on my database table that holds the record of > 300 000, recovery, and subsequently logs archive logs is generated (I did not commit the DML yet).
  
  Now my question is, how far is the whole of the archivelogs will be useful at the time of recovery, if I restore the changes? If Oracle doesn't know these archivelogs, why it should generate?
  
  And what section in the second link is correct?
  
  Help, please.
  
  Thank you
  Aswin.

  Aswin,

  Undo segments are ordinary data segments. Data segments are protected by roll forward. Temporary segments are not protected restore in progress.
  If in the case of an accident, when Oracle must retrieve a rollback segment, it will use again to recover this segment.
  In crash recovery, the first thing that will happen is rollback (Undo uncommitted changes), followed by rollforward ("readback" of committed changes).

  HTH

  -----------------
  Sybrand Bakker
  Senior Oracle DBA

• Redo log buffer question

  Hi master,
  
  This seems to be very basic, but I would like to know internal process.
  
  We know all that LGWR writes redo entries to redo logs on the disk online. on validation SCN is generated and the tag to the transaction. and LGWR writes this to online redo log files.
  
  but my question is, how these redo entries just redo log buffer? Look at all the necessary data are read from the cache of the server process buffers. It is modified it and committed. DBWR wrote this in files of data, but at what time, what process writes this committed transaction (I think again entry) in the log buffers cache?
  
  LGWR do that? What exactly happens internally?
  
  If you can please focus you some light on internals, I will be grateful...
  
  
  Thanks and greetings
  VD

  Vikrant,
  I will write less coz used pda. In general, this happens
  1. a calculation because how much space is required in the log buffer.
  2 server process acquires redo copy latch to mention some reco will be responsible.

  Redo allocation latch is used to allocate space.

  Redo allocation latch is provided after the space is released.

  Redo copy latch is used copy redo contained in the log buffer.

  Redo copy lock is released

  HTH
  Aman

• HP Elitebook 820 G3: What size of SIM card

  My new Elitebook 820 G3 has a slot for SIM card on the RIGHT side. I tried on a size full card SIM inside, but the slot is too small. What size SIM card is supposed to fit into this slot machine?

  I resolved to myself. It's a micro - a poor card.

• Portege 7100 - what size HARD drive it does support?

  Hello

  my old man (I'm a student, so no money for a new) Portege 7100 (ct) has a small hard drive, so I want to shift to a bigger... but what size HARD drive supports the 7100ct? (and that's a 1.8 "or can I use drives 2.5"?)

  thx for any help...

  Hello

  As far as I know that your unit has standard 2.5 "hard drive. Unfortunately there is no public record of such information. Accurate information, you can get that from accredited service partner or even some HARD drive supplier.
  In my opinion, your device must be able to manage with maximum up to 8 or 10 GB HARD drive. For me, we know that some offering it can manipulate the BIOS with special tools and after that BIOS recognize a much larger capacity HARD drive.

  Try to pick up some information on the net service partner or call your country. I believe that consultation service is free.

  Good bye

• HP Envy 17 t: what size usb drive is necessary for the recovery of HP Envy 17 t 10 (64-bit) Windows?

  I just installed my HP Envy and wanted to set up a recovery disk.  The USB key must be less than 32gigs, but the example has not been updated for Windows 10 the instructions say.  It shows a recovery screen for a laptop of Win8 with the source of recovery like 17 concerts.   Is there a way to check the requirements for the front to accept the HP one time recovery option.  I have a new 16 GB USB key and wanted to make sure that it is large enough.

  Also do a backup image to DVD?   If so, how many DVDs?   The laptop is new and I added only Chrome and some minor programs.  My data files are always on an external hard drive.

  Hello

  Thanks for posting in the Forum from HP Support.

  To be honest, I don't know what size will be that these recovery files are because they can vary from the version of Windows to another. They can vary from a model.

  In my opinion, 16 GB is probably not enough.

  DVDs are usually 6 (6x4.7 GB = about 28 GB) but this can vary from one model.

  This possibility of imbedding maybe once, there are other ways that you can save your system indefinitely.

  This is a free option included in all windows (creating system image, it's free as included in Vista from the outset).

  http://support.HP.com/us-en/document/c03544793

  However, this option requires (e.g. USB HDD) external HARD disk or DVD. It does not work with USB flash drives.