cache database low hit ratio (85%)

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• 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.

• How to increase! Buffer Cache Hit Ratio

  Hi all
  
  my database performance is low how to increase the buffer Cache Hit Ratio
  
  Database version: 8.1.7.0.0
  ~ Data upward since: 09:56:23, September 23, 2010
  ! Buffer Cache Hit Ratio: 81.6157
  ~ The library Cache Miss Ratio: 0.03
  ~ Dictionary Cache Miss ratio: 6.6979
  
  [Use of the shared pool] Exec time 0 seconds
  ~ Total unused Mb: 251.88
  ~ Total MB used: 98.12
  ~ MB total: 350
  ~ % Pool used: 28.04

  Buffer Cache Hit Ratio is an indicator of sense of the performance of the system.
  Are there users complain? If there are no complaints, there is also no problem.

  The best way to increase the buffer Cache Hit Ratio is executing statspack identify offensive SQL and to grant this SQL offensive.

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

• Hit Ratio in the data Caches

  Hello all-
  
  I am trying to adjust my caches, taking into account the Hit Ratio for caches. The rate of access to the cache remains constant and continuous change. When we should monitor the rate of access to caches of give me the exact number?
  
  I've seen it as much as 0.78 and sometimes its only 0.23.
  
  Please notify
  
  Thank you!

  Hello

  The answer to this question was made:- Hit Ratio in data Caches

  Ok?

  See you soon

  John
  http://John-Goodwin.blogspot.com/

• Cache - database at the request of loading

  We implement a TRADE-CACHE that stores the TRADE_ID as key and a TRADE object as the value
  I have a question related to that.
  Currently, we load the cache with only 60 days of trades and rest of the trades are in the database. I use an implementation of dumps for this cache that will load data from database in the absence of cache.
  
  I have a module in the history of trade that retrieves trades from the cache and displays them in the grid.
  I can query the history of current trade in 60 days of cache using filters. But if I need to make requests for trades more than 60 days (for example 6 months before), so how should I do? Because the filter will not raise the load method of the dumps. And I don't know the TRADE_IDs in advance for these historic trades.
  
  Did someone come on something like that? I need to know how to design the cache to handle scenarios like this
  
  Thank you!

  .. query the db for the keys, and then use them to extract the data in the cache.

  It is a model that we see used quite often, especially for when all of the data is the database and as a part of this same series of data in the cache.

  Peace,

  Cameron Purdy | The Oracle coherence
  http://coherence.Oracle.com/

• Media Cache files / Media Cache database / Scratchdisk on SSD?

  Hello

  I have a 120 GB SSD in my C: drive use.

  "Media Cache files" and "Database Cache" sit enabled by default on C: drive - which is in my case an SSD that is faster than my 7200 RPM D: drive.

  Default location of the scratchdisk is in the project plan, who are always on the 7200 RPM D: drive.

  Now my question: what files should I keep on the SSD drive - and which ones on 7200 RPM drive? The better course would be to have everything on the SSD, but the simple truth is his only 120 GB and more than half is used for etc system files already.

  I get a noticeable performance improvement if I use the SSD as scratchdisk?

  I get a noticeable performance loss if I use 7200 RPM disk for my media and Database Cache files?

  Also more information on this topic: when (any drive) are media and automatically deleted database Cache files? How does this work, because if it does delete anything automatically, after 30 projects your computer must be complete with these media Cache files...

  And the same question for the scratschdisk? Although I imagine that you must do it manually since its in the draft card anyway.

  I thank all!

  Mambo

  # The advantage of speed of SSDS is primarily marketing hype and not noticeable when editing. Comprehensive tests with conventional 8 versus 8 7200 drives SSD in a raid showed no benefit at all, in fact it was even a bit slower than conventional disks.

• Flash buttons (high, low, Hit)

  How can I add a drop shadow to a button im really confused filter?  I want the drop shadow filter to appear when I hover over the button...

  Probably the best way for you to do is to have your framework contain a movieclip and apply the filter drop shadow to this movieclip via properties only panel... no actionscript required.

• List of verification of the performance of the databases

  Hi guys,.
  
  How can you guys check that execution of the DB is healthy?
  you guys will have a list of verification that you will check all day, a weekly or monthly.
  Please share what you check in and comment on the below:
  
  Currently, we check for each month below to show that the DB is in good health:
  1. use of the Cpu memory. An increase in the CPU usage means there is an additional activity underway.
  2. for the record, the ratio of hito hides. Understand that a high rate of success does not mean that the DB is in good health. If the hit ratio is high, we will still check if there is any SQL performing a large number of logical reads that you can reduce. However, a low hit ratio means that something is wrong isn't it?
  
  We can check to prove that the DB is in good health, other than the elapsed time of SQLs? Basically need some ideas on the monthly statement of the DB health.
  
  Thank you

  Hi DBAING,

  You asked Aman Sir this issue, same im waiting for his response, but I would like to add something... First of all common full table scans for different segments could flood your buffer cache, resulting from the ageing of these pads that you could get with a cache hit, also for the index blocks which you could have found in the buffer cache. If you are truly interested in full table scans why do not bypass you the cache buffers, by going for a direct reading, use parallelism, which will read blocks directly in the PGA, but make sure you have sufficient resources like the CPU usage should be made available to you. In your case then you'd see a high value for DB FILE SCATTERED READ. Now DB FILE SCATTERED READ is a normal wait on a system well tuned. you see for the most part, but I think that this excessive wait on waiting for reading of the events can be determined only by comparison with the base line when the database was acceptable

  Now DBAING, you should find the SQL statements that take a lot of logical and physical reads. And also the readings can be caused by the cache extra undersized buffers to disk use so advise cache buffer. Because it's the sousdimensionnes buffer cache which can cause the index most recently demanding the age blocks, or even probably your wrong sql statements written causing unwanted full table.

  Now DBAING, I would warn you not be pleased with low cache hit ratio, undersized buffer cache would trigger additional entries to move Sales blocks on the disk that is run on time. So go according to the condition and be careful of other users who might find themselves with a lot of absences from the cache that could easily get access to the cache without your (REPEAT COMPLETE TABLE SCAN). And why you don't put your size segment average famous Dungeon pool. Good day

  Concerning
  Karan

• Data file Cache Vs I/O buffer

  Hello all-
  
  I lived chapter of parameters for the Ser60 cache and I have found that if my storage type is file cache settings buffered IO data is not used.
  
  I have a database that is buffering of i/o & RLE encoding and have the following cache settings:
  
  File data cache: 300000 (KB)
  Data cache: 37500 (KB)
  
  Can someone let me know if this database would be to use cache data files?
  
  If I decrease the cache of data files and increase the data cache would it effect application performance
  
  Thank you!

  If you look at the tab caches, you will see that none of your data files cache is used. in order to do no amtter what this number is.

  The cache setting affects how many blocks (uncompressed) that can enter the memory, so the encoding type has no effect on it, do not look at what data cache hit ratio in the statistics tab. If you get a low hit ratio, while you would like to consider to increase it. In addition, if you have a lot of dynamic calculations on the dense dimensions you want to increase as well.

• 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...

• Gets - Getmisses - fixed

  Dear friends,
  
  I would like to understand this SQL and what kind of results are considered as alarming and what kind of results are acceptable.
  

  select (sum(gets - getmisses - fixed)) / sum(gets) "data dictionary hit ratio"
  from v$rowcache;

  Thank you.

  The Dict data access rates
  HIT RATIO NOTES DATA DICTIONARY:

  Gets - Total number of requests for information on the data object.
  Absences from the cache - number of requests for data cache misses

  Hit Ratio should be > 90%, the increase of another SHARED_POOL_SIZE init.ora

  sys@11GDEMO > select (sum (se - getmisses - fixed)) / sum (gets) "data dictionary hit ratio."
  v $ rowcache.
  2
  hit ratio data dictionary
  -------------------------
  .978393302

  sys@11GDEMO >

• ColdFusion 11 - database cache clear

  Hello

  We have just improved a 64 bit Windows Server 2008 CF10 CF11 Update 3 and found that my previous code to clear the cached database queries no longer works as instantly or reliable as it has done previously.

  I am currently using the following code in my application.cfc file.

  This code would run if I hit the following page on the website... index.cfm? reset = yes

  < name cffunction = "onRequestStart" index = "" >

  < structKeyExists cfif (URL, "reset") >

  < cfset cacheRemoveAll() > <!---7 January 2015 has added no improvement->

  < cfset onApplicationStart() >

  < cfobjectcache action = 'Clear' >

  < / cfif >

  < / cffunction >

  Here is an example of a query, I try to clear the cache of the

  < name cfquery = "rs_Issue" datasource = "" #APPLICATION.dsource1 # "cachedwithin =" #CreateTimeSpan (0,1,0,0) #">"

  SELECT Issue_ID, Issue_Name

  OF the question

  WHERE Issue_Status = < cfqueryparam cfsqltype = "cf_sql_varchar" value = 'Current' >

  < / cfquery >

  Someone at - it suggestions of what I'm doing bad clear the cache of database (application or server-wide)?

  Thank you

  Stuart

  stuartw81 wrote:

  You may need to move from the general to the particular. By default, ColdFusion implements the query cache in a 'region' of the cache named "query". So, you should use cacheRemoveAll instead of cacheRemoveAll() ('query').

• CKPTQ in the database buffer cache and LRU

  Hi experts
  
  
  This feature can settle in cache buffers data base Oracle 10.2 or higher.
  Forums of sources: OTN and 11.2 Concepts guide
  
  According to my readings. To improve the functionality and make it more good American cache database is divided into several zones which are called workareasNow more
  
  Zoom this each activities will store multiple lists to store tampons inside the database buffer cache.
  
  Each wrokarea can have one or more then one lists to keep the wrokordering in there. The list of what each activity will have therefore to list LRU and list CKPTQ. LRU list
  
  is a list of buffers pinned, free and sales and CKPTQ is a list of stamp Sales. We can say THAT CKPTQ is a group of stamps Sales ordering of RBA weak and ready to be flushed from the cache on the disk.
  
  CKPTQ list is maintained by ordering of low RBE.
  As novice let me clearly low RBA and RBA senior first
  
  RBA is stored in the header of the block and we will give the information on which this block is spent and how many times it is changed.
  
  Low RBE: low RBE is the address to redo the first change that was applied to the block since his own last.
  RBA high: the high RBA is the address to redo the last change has been applied to the block.
  
  Now back to CKPTQ
  It can be like this (pathetic CKPTQ diagram)
  
  lowRBA = high RBA
  (Head of the CKPTQ)                         (CKPTQ line)
  
  CKPTQ is a list of stamp Sales. According to the concept of the RBA. The most recent modified buffer is at the tail of CKPTQ.
  
  Now the oracle process starts and try to get the DB cache buffer if she gets a buffer it will put an end SRM to the list.and buffer buffer LRU will become the most
  
  recently used.
  
  Now, if the process cannot find a necessary buffer.then first, he will try to find free tampons to LRU. If he finds his most he will place a datablock to the data file in the
  
  place where free buffer was sitting. (Good enough).
  
  Now, if the process cant fnd a buffer without LRU then first step would be he will find some Sales swabs at the end of the LRU to LRU list and place them on a
  
  CKPTQ (do not forget in the low order of RBA he organize it queue of CKPT). and now the oracle process will buffer required and place it on the end of the MRU of LRU list. (Because space was acclaimed by the displacement of Sales to CKPTQ buffers).
  
  I do not know of CKPTQ buffers (to be more precise tampon Sales) will move to datafiles.all buffers are line up n lower CKPTQ RBA way first. But
  
  emptied to datafile how and in what way and to what event?
  
  That's what I understand after these last three days, flipping through the blogs, forums and concepts guide. Now miss me you please erase me on and off it
  
  I can't bind the following features at this rate... It's
  
  (1) how the work of additional checkpoint with this CKPTQ?
  
  (2) now, what is this 3 second delay?
  
  (Every 3 seconds DBWR process will wake and find if nothing to write about the data files for this DBWR will check only CKPTQ).
  
  Apartment 3) form 3 second funda, when CKPTQ buffers will be moved? (IS IT when the process is unable to find any space in CKPTQ to keep buffers LRU. Its a
  
  moment where CKPTQ buffer will be moved on the disk)
  
  (4) can you please report when the control file will be updated with checkpoint so it can reduce recovery time?
  
  In many ques but I'm trying to build the entire process in mind that its operation may be I can be wrong in any phase in any stage, please correct me upward and
  
  Take me @ the end of the flow.
  
  
  Thank you
  Philippe

  Hi Aman,

  Yes, I a soft copy of ppt or white paper "Harald van Breederode" of 2009.

  -Pavan Kumar N

• Hide media and Database Cache doesn't exist in common folder, still make my full boot drive

  Hello guys,.

  I have this problem.

  I use MacBook Pro and when you work with AP, I always put scratch disk settings on my external drive. But I noticed that my mac is almost full.

  Google search, I learned that it might be because the media Cache and Cache database stacked over time. So, I tried to follow the suggested location:

  Uuse / my user/Library/Application Support / Adobe / Common

  (it's also what suggests, my settings preferably AP/media)

  the thing is, the library folder is not in the users folder, but right in MacintoshHD, so the location of the shared folder on my Mac is here:

  MacintoshHD/Library/Adobe/Common

  but there is no support at all files the folder. The only thing in common folder is Plug-ins with MediaCore folder, which is empty.

  Anyone would have to notify where my Cache of media can be?

  THANK YOU SO MUCH FOR ANY ADVICE OR YOU ADVISE.

  Paul

  Thank you. I found it.

  Please, I have just one more quick question:

  can I delete Cache media files while I'm still working on projects of the HA? Or should I expect, that all of my current projects are complete, avoiding loss of data of important project?

  THANK YOU, THANK YOU for your support,

  Paul

• Database cached own media?

  Under preferences in Premiere Pro 5.5.2 > media >

  Database cache clean media.

  What is this function and when it should be used?

  As stated in this help topic, the "Clean" button deletes these files after media Cache database Cache media files and media Cache files, for which associates source files are no longer available (for example, offline media). After reading that, we could probably expect that the 'Clean' button should delete all indexes on the database and auxiliary files (cache) associated with assets for a does not currently work on projects. However, which take place. Then, the button should actually have been called "partially own media Cache database randomly.

  Clean the media Cache database manually, i.e. remove all files in the folders as hidden media and media Cache files, not only frees up disk space by deleting the junks that are no longer needed, but also helps to fix a few problems of dynamic links or importer generic error.