CKPTQ in the database buffer cache and LRU

Similar Questions

• What else are stored in the database buffer cache?

  What else are stored in the database buffer cache, except the data reading of data files blocks?

  The nitty gritty on this point, you ask someone smarter than me waaay.

• Write the list of database buffer Cache

  What is the list of write in the database buffer cache? What is he function?
  
  Thanks in advance.

  >
  What is the list of write in the database buffer cache? What is he function?
  >
  The list of writing to dirty buffers that have not been written to disk yet.

  See "Database Buffer Cache" in the Concepts of database 11g doc
  http://docs.Oracle.com/CD/B28359_01/server.111/b28318/memory.htm
  >
  Organization of the Database Buffer Cache

  The buffers in the cache are organized into two lists: list of Scripture and the list (LRU) least recently used. List of writing contains stamps Sales, but which contain data has changed, has not yet been written to disk. The LRU list holds free buffers, pinned buffers and dirty buffers that have not yet moved to the list of Scripture. Free buffers contain no useful data and can be used. Pinned buffers are being accessed.

• clarification of term required for the DB buffer Cache

  Hello!!
  
  Here, I have a very basic conceptual question, DB buffer Cache contains the data read from the data in the file as well reduce the disk i/o of fom and oracle. If suppose that the table is constantly questioned and remains in the DB buffer cache all the time, how does oracle ensures the user gets the latest information?

  The database buffer cache is a part of the zone system Global (SGA), which is responsible for caching of blocks accessed frequently for a segment. The subsequent transactions involving the same blocks can then access them from memory, instead of from the hard disk. The works of cache buffer of database on the basis of least recently used (LRU algorithm), according to which the most frequently accessed blocks are kept in memory while the less frequent are gradually.

  See this link

  http://www.Stanford.edu/dept/ITSS/docs/Oracle/10G/server.101/b10743/memory.htm :)

• LMD are in the DB buffer Cache?

  DB version: 11.2.0.4

  OS: RHEL 6.5

  Oracle documentation defines "database buffer cache" in the following way

  "The buffer of database cache, also called the buffer cache, is the area of memory that stores copies of data in blocks to read data files"

  http://docs.Oracle.com/CD/E25054_01/server.1111/e25789/memory.htm#i10221

  Let's say that the following UPDATE statement updates 100,000 records. The server process go get all the blocks that has the matching records and place it in the DB buffer cache and updates the blocks. This change metadata are recorded in the restore log buffer by progression. At the next checkpoint changed blocks are written to the data files. Right?

  Employee UPDATE

  SET salary = salary * 1.05

  The EMPLOYEE

  WHERE deptnum = 8;

  basically: Yes, once again. Oracle has rewritten Sales buffers (i.e. buffers with different content than the corresponding blocks on the disk) on the drive under certain conditions. If the operation is cancelled, the blocks must be read again in the cache and change must be cancelled (and written).

• Question about the keep buffer Pool and the Recycle Buffer Pool

  What will be the Pool of buffers to keep and recycle Buffer Pool contains actually in the Database Buffer Cache, especially what kind of objects? I know the definitions, but need to know the practical aspects to their topic.

  918868 wrote:
  What will be the Pool of buffers to keep and recycle Buffer Pool contains actually in the Database Buffer Cache, especially what kind of objects? I know the definitions, but need to know the practical aspects to their topic.

  When all else fails, read the Fine

  http://docs.Oracle.com/CD/E11882_01/server.112/e16638/memory.htm#PFGRF94285

• Concept of database buffer cache

  Being a newbie, s/n, I learn Oracle Architecture through Database Buffer Cache in SGA, and it's different parts such as buffer pinned, blocks Sales & buffer. Bookish language seems to be a bit complex. So it will be great if someone here can find little time to help me understand the Database Buffer Cache & it's components and features in a simple and brief language.
  
  All entries of my friends here will be highly appreciated.
  
  Published by: 916438 on March 24, 2012 23:19

  916438 wrote:
  I went through the links, just a question - what is the difference and the relationship between dirty buffer and pinned?

  A dirty buffer is an image modified to the buffer that was made originally in memory. I will give an example that a buffer contains a value of 10 to the disk. Later, this buffer was consulted and was introduced into the buffer cache and with an update of the order was changed to 11 (no validation emitted again). Since it is a modified image of the buffer that was originally in the memory, it is called dirty buffer . Concept of pinning meaning essentially access to and since then a buffer is pinned, it will not be sued by the buffer cache flushing algorithm. To access a buffer for what anyone, query or change, it must be consulted or pinned. A buffer can be made dirty when you pin first.

  HTH
  Aman...

• UNIX buffer cache vs oracle database buffer cache

  1. What is the difference between the operating system buffer cache and the oracle buffer cache?
  2. in what cases, oracle uses oracle buffer cache? in this case, oracle does not use buffer cache instead of use the OS buffer cache.
  
  I'm confused about this concept.
  
  Appreciate any help.
  
  S.

  Database instance does not use the OS buffer cache in 2 cases:

  1 FILESYSTEMIO_OPTIONS is set to ARM or SETALL (see http://download.oracle.com/docs/cd/E11882_01/server.112/e16638/os.htm#PFGRF94412).

  2 database instance uses ASM with raw devices.

  Edited by: P. Forstmann on July 19. 2011 18:43
  It is not ASM with ASMLib but ASM with gross as devices explained ASMLib and Linux block devices

  Edited by: P. Forstmann on July 19. 2011 19:36

• Upgrade the database to 8i and 9i and 10g and 11g

  Nice day
  
  Hi all
  
  Please can someone help me to get a good document for the upgrade of the database to upgrade the database to 8i and 9i and 10g and 11g include prerequisites and upgrade processes and after upgrading the process waiting for your response because it required required

  http://download.Oracle.com/docs/CD/B19306_01/server.102/b14238/TOC.htm

  Concerning
  Asif Kabir

• DB file sequential reads on the table scan complete and LRU (new)

  I would like to add a question on the subject

  scan of full table and LRU

  According to MOS doc ument 1457693.1

  «.. signs diluvium readings of the caching blocks can be divided into a number of small multiblock and self-contained bed. »

  The question is if sequential readings of db file submitted by a FULL SCAN operation will be cached on LRU or MRU list?

  I'm afraid the flushes of heat/floods the buffer cache with a lot of FULL SCAN db file sequential reads.

  For which direct path series reason readings will be inapplicable, so using this new feature of 11g is out of scope for this question.

  Thank you for your interest,

  Rainer Stenzel

  There are a few different patterns of behavior depends on the size of the table (relative to the size of the buffer cache), but the key question is probably "readings will increment the counter of touch" - because if they are not the blocks will fall the LRU list fairly quickly, if they do then the blocks could (after a few tablescans) eventually be promoted in half hot from the cache.

  I did some quick tests (that requires a little care in the Installer) which suggest the number touch was not incremented has therefore not had any effect on the question of if the block would get preferential treatment when they have reached the end of the LRU.

  I'm a little puzzled by your expression: "cached on LRU or MRU list" - it's not two different lists; but people talk about "the end of the MRU of the LRU list.

  Concerning

  Jonathan Lewis

• Read data larger than the DB buffer Cache

  DB version: 10.2.0.4
  OS: Solarit 5.10
  
  
  We have a DB with 1 GB for DB_CACHE_SIZE. Automatic shared memory management is disabled (SGA_TARGET = 0).
  
  If a query is triggered on a table that will grab the 2 GB of data. Hang in this session? How oracle handles this?

  Tom wrote:
  If the recovered blocks get automatically removed from the buffer cache once it is retrieved by the LRU algorithm, then Oracle must handle this without any problem. Right?

  Yes. No problem in that the "+ a fetch size +" (for example, by selecting 2 GB with a value of lines) need to fit completely in the db (only 1 GB in size) buffer cache.

  As mentioned Sybrand - everything in this case is emptied as blocks of data more recent will be read... and that emptied shortly after thereafter as of the even more recent data blocks are read.

  The ratio / access to the cache will be low.

  But this will not cause Oracle errors or problems - simply that degrade performance as volumes of data being processed exceeds the capacity of the cache.

  It's like running a very broad program that requires more RAM which is available on a PC. The 'additional RAM' is the file on the disk. The APA will be slow because its memory pages (some disk) must be swapped in and out of memory as needed. It will work faster if the PC has an enough RAM. However, the o/s is designed to address this exact situation that requires more RAM than physically available.

  Similar situation with the treatment of large chunks of data than the buffer cache has a capacity of.

• Database buffer cache hit ratio is less than 90%

  Hi all
  
  For the following query I get the bottom 90%
  
  SELECT ROUND (((1-(phy.) VALUE /(cur.) VALUE con. ((VALUE))) * 100), 2) "HIT RATIO" +.
  OF SYS.v_$ sysstat news,.
  SYS.v_$ sysstat con,.
  SYS.v_$ sysstat phy
  WHERE cur.NAME = 'db block gets. "
  AND con.NAME = "becomes" compatible
  AND phy.NAME = 'physical reads. "
  
  RATE
  ----------
  81,79 +.
  
  Please advice me what could be the reasons and how do I make more than 90%.
  I have access to metalink. I raise this issue with Oracle metalink?
  
  Thank you and best regards,
  Arun Kumar

  user8853422 wrote:
  I'm afraid I can't do that... because I'm still new to DBA... What is my understanding that if buffer cache hit ratio is high, it means that server process do not need to recover data from data files, instead it will look in the buffer cache. Time is less and therefore better performance.

  Your understanding is "basically" correct.

  Please correct me if I'm wrong.

  However, your understanding is limited to a set of very specific circumstances. In reality there are times where it may be reasonable to pick up the disc.

  Basically, the concept of a specific BCHR is excellent if you have exactly the same kind of question asked time and time again (limited OLTP) ensure that guests have repeatedly looking at things in memory, or if you have enough memory to fit the entire database AND all potential read consistent blocks in the SGA.

  Anything less and you're looking at compromises.

  And that 'compromise' requirement that throws the usefulness of the BCHR whack. You need to look at the complete picture.

  Therefore, we can honestly say: If you follow your buffer Cache Hit Ratio over a period of time and your workload (transaction rate, type of transaction and competition) remains about the same, then you could grant using BCHR or use it as an indicator of the health of your system.

  But watch the BCHR and say, "this number is good" and "this number is bad" is essentially meaningless.

• Quality of the data buffer Cache

  Hi all
  
  Can someone please please tell some ways in which I can improve the quality of data buffer? He is currently at 51.2%. The DB is 10.2.0.2.0
  
  I want to know all the factors of wat should I keep in mind if I want to increase DB_CACHE_SIZE?
  
  Also, I want to know how I can find Cache Hit ratio?
  
  In addition, I want to know which are the most frequently viewed items in my DB?
  
  Thank you and best regards,
  
  Nick.

  Bolle wrote:
  You can try to reduce the size of the buffer cache to increase hit ratio.

  Huh? It's new! How would it happen?
  Aman...

• Firefox crashed after attempting to clear the browser's cache and cookies, and now it crashes everytime I open.

  Update: I used the wrong word in the question. It FREEZES rather than be crushed. I have to force quit. Hope this clear things upward.

  I followed the instructions of an officer of Yahoo Mail (in a problem of yahoo with their mail) to clear the cache and cookies on 'Everything' (time slot). Crashed Firefox. Now every time that I reopen it, it gives the error message and an option to restore or start a new session, but as soon as I click on anything, whether it crashes.

  Apparently, my user profile has been altered. Deleted file Profiles , dumped FF, did a clean install and it works like a charm. I saved profiles, but I'm scared to have to add because I don't know what is corrupt. It seems my attempt to clear the cache and cookies trigger something...

• change ip address of the database servers primary and standby

  Hello.

  I have an oracle server primary and backup (version 11.2.0.4) on windows 8 profesional.

  They work well until today.

  Today, I had to change my ip address on both servers.

  After that I changed the ip address of the OS, I changed the ip address in tnsnames.ora and listener.ora files only.

  A moment that everything worked well. But now the archivelog files not copy to the standby server.

  Is there a place where I have to change ip or the settings on the database?

  Please, I hope you can help me.

  Best regards

  Hello

  After that I changed the ip address of the OS, I changed the ip address in tnsnames.ora and listener.ora files only.

  A moment that everything worked well. But now the archivelog files not copy to the standby server.

  1. If it worked for a while after the change of ip address

  3. make sure your journal alerts, what it says? information about the error?

  2. first thing ipadress sequenced in tnsnames.ora and listener.ora on primary and standby

  3. check ping to the host-level work and tnpsing is reached or not. If both are working check listeners are up or not and they are able to identify the services of db, registered or not.

  4. now, connect as sysdba password on the servers file

  5 check v$ achive_Dest_status for valid or relevant destination which is assistance for the transfer of the archives of primary Eve (the error column)

  -Not especially to knew what the problem is, you should get the controls.

  -Pavan Kumar N