Cache HIT Ratio Problem
Jul 23, 2005
Hello
I am tring to figure out why our SQL server is a bit sluggish from
time to time.
It is running a dual XEON, with 2.5 GB RAM, and a fast SCSI I/O sub
system setup as follows.
OS, mirrored 2 drives
SQL DATA 16 HDD RAID 10
SQL LOG 4 HDD RAID 10
SQL tempdb 4 HDD RAID 10
OS = win 2003
SQL = sql2000 standard edition
dbcc showcontig shows me nothing special, it looks ok
I launch performacne monitor and add SQL server cache manager: hit
ratio
and it is constantly at 7% and never changes up or down, it is just
constant.
Can this be correct? and if so it sounds rather bad, we have a
handfull of large tables that are heavily used and enough RAM to hold
them all in RAM so I really do not understand why the cache hit ratio
is not higher.
Any hints would be great
rgds
Matt
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Mar 13, 2003
On Microsoft performance monitor, what is the difference between SQL Server Cache Manager: Cache Hit Ratio and SQL
Server Buffer Manager: Buffer Cache Hit Ratio? We have a production server where the buffer cache hit ratio is
consistently at 99%, which is normal. However, the cache hit ratio is 73%. What is the difference between the two
hit ratios, and why would we have such a significant difference between the two?
Any help or advice would be much appreciated.
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Sep 18, 2000
I have been seeing this strange statistics in one of our servers. The cache hit ratio has gone beyond 100%, it is currently showing 124%. Has anyone seen this before.
Thanks
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Mar 18, 2005
I have a large dell server with 4 processors, and 8 gig of memory on win 2000 advanced with sql 2000 enterprise edition running a 3rd party app. My cache hit ratio averages about 76%. I thought the gneral rule was if you get below 80% to add more memory. However my memory manager shows I am only using 71% of my memory and have a full gig available. I have the sql server set to use about 7.1 gig of the 8 gig on the server. My ? is if I am only using 71% of my memory, will will adding more memory actually help my cache hit ratio
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Jan 2, 2004
Does anyone know how to measure the buffer cache hit ratio? I have been reading a lot about it but can't find this measurement in Performance Monitor.
Thanks
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May 5, 2004
Maybe I am just a lot better at this than I thought, but I figure that somewhere there is a mathematical rule that is being overlooked. When I run dbcc sqlperf (lrustats) on some of my production machines, I sometimes end up with a cache hit ratio (which is defined as a percentage, mind you) that is slightly over the limit:
Statistic Value
-------------------------------- ------------------------
Cache Hit Ratio 100.00898
Cache Flushes 0.0
Free Page Scan (Avg) 0.0
Free Page Scan (Max) 0.0
Min Free Buffers 331.0
Cache Size 4362.0
Free Buffers 9434.0
I suspect some counter somewhere is getting wrapped around its 4 byte limit. Is there any reliable source for getting statisics about SQL Server performance? Users tend be unreliable and say everything is slow.
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Jun 20, 2014
I'm putting together some monitor scripts, have buffer cache ratio etc etc but struggling to get an accurate script for the current procedure cache hit ratio...
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Jul 16, 2015
What is better values for Buffer Cache Hot Ratio in SQL Server 2012. Is the values changed from 2008r2 to 2012?
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Jun 19, 2008
I am wondering if 100% buffer cache hit ratio is considered not good in general?
Are there instances that it is actually bad and can contribute to server performance degradation?
Any thoughts on the topic most welcome :)
--------------------
keeping it simple...
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Jul 23, 2005
This issue just happen recently. The buffer cache ratio went from > 90%to 50% and has slowly been climbing back up over 8 hours or so. Itscurrently @ 76%. Is this something I should take action on immediately?It seems to be coming back to normal...
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Sep 1, 2006
HiI have trouble with MSSQL2000 SP4 (without any hotfixes). During last twoweeks it start works anormally. After last optimalization (about few monthsago) it works good (fast, without blocks). Its buffer cache hit ratio wasabout 99.7-99.8. Last day it starts work slow, there was many blocks anddedlocks. There are no any queries, jobs and applications was added. Nowbuffer cache hit ratio oscilate about 95-98. I try update statistics andreindex some hard used tables, but there is no effect or effect is weryshort (after few hours problem return).Mayby somene know what it could be?Is it possible to estimate how each table (using DBCC SHOW_STATISTICS orDBCC SHOWCONTIG or others) how the table affect on total buffer cache hitratio?Marek---www.programowanieobiektowe.pl
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Sep 12, 2014
Our server administrator forwarded some messages from SCOM that indicate:
SQL DB Engine 2012 Page Life Expectancy and Buffer Cache Hit Ratio is too low
When I logged into the offending server, I could not find anything in the SQL Log File that indicates this.
I was wondering how did SCOM identify this issue - where in SQL Server would this have been reported to SCOM?
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Dec 27, 2007
Im getting this error when trying to set up a cache dependency...are there any special permissions etc?From CS:SqlCacheDependency dep = new SqlCacheDependency("MySite-Cache", "Products");Cache.Insert("Products", de.GetAllProductsList(), dep); From connectionStrings.config:<add name="SiteDB" connectionString="Data Source=localhost,[port]SQLEXPRESS;Integrated Security=true;User Instance=true; AttachDBFileName=|DataDirectory|ASPNETDB.MDF" providerName="System.Data.SqlClient" />Also tried this using my machinename<add name="SiteDB" connectionString="Data
Source=<machinename>,[port]SQLEXPRESS;Integrated Security=true;User
Instance=true; AttachDBFileName=|DataDirectory|ASPNETDB.MDF"
providerName="System.Data.SqlClient" /> From web.config: <caching> <sqlCacheDependency enabled="true" pollTime="10000"> <databases> <add name="MySite-Cache" connectionStringName="SiteDB" pollTime="2000"/> </databases> </sqlCacheDependency> </caching> EDIT: So making progress I can't seem to get the table registered for cache dependency:The sample i have says"aspnet_regsql.exe -E -S .SqlExpress -d aspnetdb -t Customers -et"and the command line response is "Enabling the table for SQL cache dependency..An error has happened. Details of the exception:The table 'Customers' cannot be found in the database."Where does this "Customers" table come from? There is obviously not an application specific "Customers" table in aspnetdb I'm confused probably more by the example than anything....
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May 31, 2007
Is there a way to drop clean buffers at the database level instead of the server/instance level like the undocumented €œDBCC FLUSHPROCINDB (@dbid)€??
Is there a workaround for €œdbo€? to be able to flush procedure and data cache without being elevated to €œsysadmin€? server role?
PS: I am aware of the sp_recompile option that can be used to invalidate cached execution plans.
Thx.
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Feb 15, 2008
Hi guys,
I am looking at the plan caches/cached pages from the perspective of
sys.dm_os_memory_cache_counters and sql serverlan Cache - Cache Pages
For the first one I am using
select (sum(single_pages_kb) + sum(multi_pages_kb) )
from sys.dm_os_memory_cache_counters
where type = 'CACHESTORE_SQLCP' or type = 'CACHESTORE_OBJCP'
a slight change from a query in
http://blogs.msdn.com/sqlprogrammability/
For the second just perfmon.
The first one gives me a count of about 670,000 pages only for the object and query cache and the second one gives me a total of about 100,000 pages for five type of caches including object and query.
If I am using the query from http://blogs.msdn.com/sqlprogrammability/ to determin the plan cache size
select (sum(single_pages_kb) + sum(multi_pages_kb) ) * 8 / (1024.0 * 1024.0) as plan_cache_in_GB
from sys.dm_os_memory_cache_counters
where type = 'CACHESTORE_SQLCP' or type = 'CACHESTORE_OBJCP'
it gives me about 5 GB when in fact my SQL Server it can access only max 2GB with Total and Target Server Memory at about 1.5 GB.
Does anyone have any idea what is going on?
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May 21, 2008
Hello,
I have a calculated member that is a ratio calculation. It works fine but I would like that the value for the "All" member to be the sum of the children.
So I have the following MDX where the calculated member [Dim Group Rubric].[Group Rubric Description].[BO + ADM Cost] does not give me good results for the "All" member:
WITH
MEMBER [TOTAL YEAR CONTRACT] AS sum({[Total Year]},[Dim Contract].[Contract Number].[563131])
MEMBER [TOTAL YEAR BU] AS sum ([Total Year])
MEMBER [Dim Group Rubric].[Group Rubric Description].[TOTAL BU PVN] as
([Dim Group Rubric].[Group Rubric Description].[PVN], [TOTAL YEAR BU])
MEMBER [Dim Group Rubric].[Group Rubric Description].[TOTAL BU BO + ADM] as
([Dim Group Rubric].[Group Rubric Description].[BO + ADM], [TOTAL YEAR BU])
MEMBER [Dim Group Rubric].[Group Rubric Description].[BO + ADM Cost] as
([Dim Group Rubric].[Group Rubric Description].[PVN], [TOTAL YEAR CONTRACT])
/ ([Dim Group Rubric].[Group Rubric Description].[TOTAL BU PVN], [TOTAL YEAR BU])
* ([Dim Group Rubric].[Group Rubric Description].[TOTAL BU BO + ADM], [TOTAL YEAR BU])
SELECT
NON EMPTY {[TOTAL YEAR CONTRACT],[TOTAL YEAR BU]}
ON 0,
{[Dim Group Rubric].[Group Rubric Description].[BO + ADM Cost]}
*
UNION(
[Dim BV Organisation Finance].[Business Unit].[All]
,FILTER(
[Dim BV Organisation Finance].[Business Unit].children
,[Dim BV Organisation Finance].[Business Unit Code].currentmember.name
= '071MIND1'
)
,FILTER(
[Dim BV Organisation Finance].[Business Unit].children
,[Dim BV Organisation Finance].[Business Unit Code].currentmember.name
<> '071MIND1'
)
)
ON 1
FROM (SELECT ([Dim Year].[Year].&[2008]) ON 0
FROM (SELECT ({[Dim BV Organisation Finance].[Business Unit Code].[071MIND1]
,[Dim BV Organisation Finance].[Business Unit Code].[071DIDD1]}) ON 0
FROM [BV Contract Margin DW]))
When I launch this query I obtain:
TOTAL YEAR BU
BO + ADM Cost All - 45013 (I would like to obtain here - 90651)
BO + ADM Cost 071MIND1 - 35680
BO + ADM Cost 071DIDD1 - 54971
Please do you know what should be changed in this query to obtain the good results?
Thanks.
Guillaume
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Nov 14, 2007
I have to get the ratio like A:B with two calculated columns. A and B both are the counts of the rows.
Please help me with this, it's really urgent!
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Oct 16, 2007
Can anyone pls help me to solve my problem in SSRS. Also I wanted to plot the 'Ratio' in to a chart against the 'Year'.
The scenario is:
Year Amount_A Amount_B Ratio(Amount_A/Amount_B)
05 x y x/y
06 a b a/b
07 m n m/n
Its very needy.
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Oct 28, 2015
How do I author a SQL Query which meets the following requirement: Display a ratio of (instances where status is a success)/(instances where status is a success or instance is a failure). The below syntax is incorrect. However, I hope to beter explain what I am trying to accomplish using the incorrect SQL query below.
SELECT SUM(Case When Status = "SUCCESS")/SUM( Case When Status = "FALLBACK")
FROM ruleResults;
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Dec 1, 2014
I am doing some work in microstrategy reports and using SQL data cube. I am creating a summary report (Counting on Unique ID) in MS where when I put in a particular attribute/column from cube it splits the data count down into 2 separate values that I have defined in the select case statement of the SQL query.
I want to work out a ratio of the count unique ID between these two values but can't do this in MS report as it is not a physical column but summary split of data.Is there a way I can do this in SQL? My summary looks something like this:
N E
====================== =========================
**Y** N **Y** N
========= ========== ========= =========
570 140 89 56
Where the Y/N field is the one I have split down against the N/E column. I want to work out ratio between the 2 "Y" fields but in SQL. Here is a SQL example snapshot of my data:
Unique_ID New/Existing Application Attend_Interview
========= ======================== ================
12554445 E Y
65766879 N N
53375654 N Y
44323224 E N
93656786 E Y
wondering if I might be able to do a procedure or similar or something more dynamic in SQL query?
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Sep 26, 2000
Hi,
In m*y SQL server 7.0,
when using Performance, I see in graph: Buffer Catche Hit Ratio Counter
(SQLServer Buffer Manager objects)always is maximum (100). What does this mean ? What's the Buffer Catche Hit Ratio?
How do I configure SQL server to performance?
Thanks in advance.
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Oct 30, 2015
I'm collecting performance data via DMV to check the buffer hit ratio on several servers. Sometimes I get values high above 100% hit Ratio.
Example (50050%):
SQLServer:Buffer Manager:Buffer cache hit ratio 2002
SQLServer:Buffer Manager:Buffer cache hit ratio base 4
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Aug 31, 2015
I am checking some ratio numbers for our system engineers, those are
Read/write ratio?
Random/sequential ratio?
Read/write block size?
For Read/write ratio, I am using below query,
SELECT
m.type_desc
, CEILING(sum(num_of_bytes_read*1.0) / (sum(num_of_bytes_read*1.0) + sum(num_of_bytes_written*1.0)) * 100) AS 'Read %'
, CAST((sum(v.size_on_disk_bytes) / 1024.0 / 1024 / 1024) AS MONEY) AS 'FileSizeGB'
[Code] ....
Random/sequential ratio, I googled but cannot find a similar query to get the result?
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Nov 20, 2015
Sample Query :
SELECT 'A' [Type], 1 AS [NUMERATOR]Â Â Â Â , 2 AS [DENOMINATOR]
UNION ALL
SELECT 'B' [Type], 2 AS [NUMERATOR]Â Â Â Â , 4 AS [DENOMINATOR]
UNION ALL
SELECT 'C' [Type], 3 AS [NUMERATOR]    , 6 AS [DENOMINATOR]
[Code] ...
I need to show the ratios beside each bar (shown in red)Â as shown in the above diagram.
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Jun 11, 2015
I'm trying to use the Ratio to Parent sproc - [URL] .... The problem is that the stored proc appears to be pegged at 4 decimal places (which translates to ##.##%). This is losing precision and isn't adding up to 100% when the ratios are summed individually.
Can this be fixed within SSAS or will i need to modify the assp code? .NET decimals are meant to automagically scale, so not sure why it's coming out as (5,4) but my .net coding knowledge is fairly poor.I get the correct behaviour if hardcode a ratio to parent MDX calc (the resulting ratio has as many decimal points as are required)
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May 22, 2015
I created a PowerPivot measure which is a ratio Ratio = Number of Events/Time calculated on 12 months. I would like the grand total to be this Rate Sum(Number Of Events)/Sum(Time calculated).
In my Pivot I have one measure which I called Value and this value can have different types depending on one attribute.For instance one attribute is number of events, an other one is time and the third one is ratio.I want to display a custom grand total simple sum for events and time and a calculation of my ratio for ratio.
For instance
                            201501 201502 201503 TOTAL
Number of events           8        10        10    28
Time                             5           5        Â
4Â Â Â Â 14
Ratio                           8/5      10/5     10/4 28/14
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Jul 23, 2005
Just wanted to know what is a general rule of thumb when determining log file space against a database's data file.We allow our data file for our database to grow 10%, unlimited. We do not allow our log file to autogrow due to a specific and poorly written process (which we are in a three month process of remove) that can balloon the log file size.Should it be 10% of the Data file, i.e. if the Date file size is 800MB the log file should be 8MB?I realize there are a myraid of factors that go against file size but a general starting point would be nice.ThanksJeff--Message posted via http://www.sqlmonster.com
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Jul 12, 2006
I read about the SQL 2005 Buffer Cache and the .NET cache.I tried it on about 8000 users query. Both are fast....SQL 2005 being a little faster (probably due to I was sorting the .NET Cache).Any comments?
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Jul 9, 2002
Hi there,
We have cluster server and we are using sql server 7, everything was working fine on node a and when we move to node b and run the job from the jobs it gives the error message:
Error 22022:SQLServerAgent Error: job ox7bb7d7bf23b8974d8ea8f15e43e854cf
does not exist in the job cache
Can anyone help on this.
Thanks in advance.
Madhu.
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Dec 3, 2001
In Sybase, I can bind a database or table to cache, can I do the same
on SQL 7.0?
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Sep 9, 2005
Hi..
I don't know this is possible or not.
for example.. I have a blog site..
my entry links are like that
blog.asp?ID=33
blog.asp?ID=36
36 points "select * tbl where id=36"
And approximately BLOG #36 has 400 views everyday..
content is same.It never change..
Everyday my application performs "select * tbl where id=36"
with direct ASP or Stored Procedure..
Do you have any solution about this ?
How to improve performance..
Just imagine, If entry #36 had 2.000 views everyday ?
just example..
Of course the less perform query, the more performance..
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Mar 14, 2008
Hello!
When I create new job, I get a message "Job cache 97% full"
What should I do? And what IS a job cache?
Thanks!
Makkaramestari
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Apr 25, 2007
Hi all,
I have a question regarding SQL caching.
I want to use SQL caching for my pages.I've gone through http://msdn2.microsoft.com/en-us/library/e3w8402y(VS.80).aspx article on msdn, where in step by step procedure is explained for this. But I have a slightly different situation. In the article, we need to configure our application from web.config by following...
<!-- caching section group --><caching> <sqlCacheDependency enabled = "true" pollTime = "1000" > <databases> <add name="Northwind" connectionStringName="NorthwindConnectionString1" pollTime = "1000" /> </databases> </sqlCacheDependency></caching>
Where in "NorthwindConnectionString1" is the SQLdatasource connection string. But I'm not using SQLDatasource, and have my own classes to build a connection datasource and get a dataset, and then bind it to my control.So in this case what should I write for the above "connectionstring" attribute. My connection string is in web.config only with a section defined. and in my application i'm reading from web.fing only.The connection section i'm using is as follows...
<ConnSettings>
<add key="ConnString" value="server=serverName;database=dbName;uid=dbuser;Pwd=password"/>
</ConnSettings>
I want to know how to configure my sql cache in this situation.
Thanks,
Mehul Mistry
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