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?
I'm getting an alert which states that both my Buffer Cache Hit Ratio and PLE are low on one of my SQL Servers though I'm not sure how to correctly check this.
I ran:
SELECT object_name, counter_name, cntr_value
FROM sys.dm_os_performance_counters
WHERE [object_name] LIKE '%Buffer Manager%'
AND [counter_name] = 'Buffer cache hit ratio'
Which gives me the Buffer Cache Hit Ratio, cntr_Value of 9 though its constantly dipping between 3-3000 and is never steady and I'm unsure if this is normal.
I also ran:
SELECT object_name, counter_name, cntr_value
FROM sys.dm_os_performance_counters
WHERE [object_name] LIKE '%Buffer Manager%'
AND [counter_name] = 'Page life expectancy'
Which gives me the Page life expectancy of 209061.
If these values would cause concern and if this is a normal Buffer Cache Hit Ratio? It's constantly dropping from high or low from what I can see. These scripts were pulled from another forum and I'm assuming they're showing the correct values.
I have few servers that are VM and different version of SQL Severs (2008 Express/Standard, 2012, or 2014 Enterprise) and seems all of them have same issue that when I am querying "sys.dm_os_performance_counters" for "[object_name] LIKE '%Buffer Manager%' AND [counter_name] = 'Page life expectancy'" I am getting very big number (Ex, above 100K or some servers 1M).Is this number seems fine or acceptable?Â
View 6 Replies View RelatedI measure PLE on my server and insert them every minute into a table. Now, when I look into the table I just dont know how to interpret the following data. I dont understand how is that possible. It's an sql server bug? or? How to interpret that data?Â
View 10 Replies View RelatedI started receiving these alert messages, and after doing some re-search still can't figure out how to totally resolve it. From what I gather the value Microsoft stipulates 300 for PLE is not accurate if you running a 64 bit OS and dependent of the amount of RAM you allocate to SQL.
If I allocate 20 Gig of RAM to SQL, The PLE should not drop below 1500 - (PLE should be 300 for every 4 GB of RAM) (20/4)*300
During the course of the day it sometimes drops below 1500, so my question is how can I further see why and what query is causing this to happen???
I setup a monitoring job as mentioned by Steve Hood to capture results for me every 20 min.
What is better values for Buffer Cache Hot Ratio in SQL Server 2012. Is the values changed from 2008r2 to 2012?
View 2 Replies View RelatedIn my MSSQL server 2000 sp4, in performanece monito, buffer memory, pagelife expectancy is equal to 0.00000 (average for 10 sec, auto update). Ithink sth is wrong configured, but what?Marek
View 1 Replies View RelatedSTUCK! I have a consistent PLE value of 0. The server has 8GB RAM, I/O-CPU counters under 30%, various DMV's results show the buffer and memory cache do not calculate up to it's AWE (32-bit) allocation 7.5GB, waits don't show any problems, no locks, no blocks.
There are improvements to indexes that have to be made but where can I identify the root cause to the low PLE? The same process runs x6 quicker on 2 other much lower spec SQL servers exact copies from a data prospective, however there PLE is very high and not production.
Any ideas?
Page Life Expectancy (PLE) is pretty bad on my server. PLE is hovering around 3 minutes "sometimes" but is usally around 20-30 seconds.
Total memory allocated to SQL ( a fixed amount ) is set at 3GB.
Of the total memory allocated, SQL Server is using 2.52GB ... so there is room if needed.
The Buffer Cache is sitting at 2.09GB with a hit rate around 99.8%.
The Procedure Cache is sitting at 378MB with a hit rate around 90.5%.
CPU is hovering around 10-20%
Free System Page Table Entries is LOW ... at 22343
Disc Queue Lengths spike quite often to above 5 and sometimes as high as 36. Usually sitting at .05 to 1.0 (and there are times when the DQLs are great and not measureable.
What I need to find out is how to get PLE above the recommended 5 minute mark???
Please let me know if there are any other items I need to note.
Thanks!
=========================================
Here are some hardware/Software/Implementation stats:
=========================================
SQL Server 2005 Standard w/ latest patch of 3152
Windows Sever 2003 R2 Standard w/ latest patches applied (says PAE is enabled in the System Properties.. General tab
4 Intel Xeon X5355 @266GHz
4GB RAM with 3GB dedicated to SQL Server via the /3GB switch
System Disc ( C: ) is 136GB (free space is 122GB) and is RAID10
Data/SQL Disc ( G: ) is 408GB (free space is 347GB) and is RAID10
The SQL files (MDFs/LDFs, TempDB, DB & TLog backups, SQL application and all that is SQL related) are all on the single array (G (** which I must note is NOT how I configured the SQL environment but aquired the setup when I started the position).
Every day, at same hour, my SQL Server is showing error of PLE less than 300 seconds.
So after this, the server works properly.
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
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...
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...
View 1 Replies View RelatedHiI 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
View 1 Replies View RelatedI'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
I've a spatial (GIS) Data which is used frequently insertion, updation.
5 lakh records insertion in daily basis. when I trying to generate reports last 3 days or one weak, it takes 20-30 minute.
very disappointing while playing with clients. how to boostup and perform fast.
I think as so once we set query plan in buffer permanently then i would be faster than ever.
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.
We are troubleshooting a performance problem and the test result is slow the 1st time but the subsequent runs are faster.. Logging out of application and log back in ( connecting to a new database session) did not clear the buffer cache as I thought it would.. When does the database clear the buffer cache? Is it not per database session?
I can issue CHECKPOINT and then run DBCC DROPCLEANBUFFERS to clear the buffers in the disk. But since we are testing from the application,do we need to run these commands via application code to clear buffer/per database session OR can we run these commands from a management studio session?
I have a virtual server (VMware ESX) with 64GB RAM running a single instance of SQL 2012 SP1. The max memory config is set to 59392 (58GB).
The Page Life Expectancy for this server has been averaging well under 10 mins for the last few days, according to our monitoring.
I have been checking the amount of data in the buffer cache periodically during the day with the below query, which seems to show that there is never more than about 10GB of data at any one time, frequently dropping below 5GB:
SELECT COUNT(*) AS BufferPages,
CONVERT(decimal(10, 2), COUNT(*) / 128.0) AS BufferMB
FROM sys.dm_os_buffer_descriptorsWhy would the amount of cached data be so low (and cause so much churn)?
I am aware that other things will require some of that memory (plan cache etc.) but with Max Mem of 58GB, I would expect there to be a much higher amount of actual cached data at any one time. I did the same checks on another VM with the same amount of RAM/Max Mem setting, and there was 50GB of data in the cache, with PLE measured in hours.
I am using SQL 2012 and I am trying to find buffer cache usage by DB objects within a particular DB.
I am running the following query
select
name as DB,
objname as db_object_name,
COUNT(name) as cache_page_count,
COUNT('x')*8.0/1024 as size_mb
[Code] ....
Following are the results:-
DB db_object_name cache_page_countsize_mb
TEST_DBNULL 428 3.34375
TEST_DBsysobjvalues 369 2.882812
TEST_DBsyscolpars 44 0.34375
TEST_DBsysssislog 38 0.296875
....
.....
Question- Why am I getting 428 pages for which there is no corresponding DB object? Why are so many pages present in sys.dm_os_buffer_descriptors but are missing from sys.allocation_units.
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.
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
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
View 5 Replies View RelatedHelloI am tring to figure out why our SQL server is a bit sluggish fromtime to time.It is running a dual XEON, with 2.5 GB RAM, and a fast SCSI I/O subsystem setup as follows.OS, mirrored 2 drivesSQL DATA 16 HDD RAID 10SQL LOG 4 HDD RAID 10SQL tempdb 4 HDD RAID 10OS = win 2003SQL = sql2000 standard editiondbcc showcontig shows me nothing special, it looks okI launch performacne monitor and add SQL server cache manager: hitratioand it is constantly at 7% and never changes up or down, it is justconstant.Can this be correct? and if so it sounds rather bad, we have ahandfull of large tables that are heavily used and enough RAM to holdthem all in RAM so I really do not understand why the cache hit ratiois not higher.Any hints would be greatrgdsMatt
View 9 Replies View RelatedHi,
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.
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.
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...
View 1 Replies View RelatedHelp, have recently upgraded from 6.5 to 7.0 and have come across a problem with performance. The problem appears to relate to the buffer cache being flushed, the buffer cache hit ratio drops from 98% to 0% in a matter of a second. It then very slowly grows, then is flushed again, then increase slowly upto 30%.
Does any one have any ideas as to what would flush the buffer cache?
Any comments would be much appreciated - cheers
Hi,
My problem is that I cannot completely clean buffer cache on SQL Server 2005 version 9.00.2047.00 (probably SP1).
Right after I run DBCC DROPCLEANBUFFERS in the context of my database (this is development server, and so far I am only the one who is working with a particular database), I run a script that quetries sys.dm_os_buffer_descriptors view also from the context of my database to make sure that the buffer cache is really clean. However it shows large number of entries totalling 42 MB.
I ran both DBCC an the script in the past too, and it always showed nothing in the results, that means that buffers were really clean. The reason why I am running this is for benchmarking of existing and new application.
Does anybody have any idea, suggestions, how to troubleshoot this issue ? I already closed all connections to this database, but rebooting the server is not an option since other people are also working on it.
Thanks
Hello,
Does the performance counter Buffer cache object refer to Data cache and procedure cache or just refers to Data cache???
I was of the opinion that Buffer cache means data cache and Plan cache means procedure cache. Can someone throw some light???
Regards
Jaideep
How do i check the size of the datacache allocated from the buffer pool by sql server?
DMV or anything to show me the pool allocation sizes for the various pools in sql server i think i may be able to work from there.
Extending the buffer pool onto an SSD drive that is shared ? For instance, if we had a mirrored system drive(The C logical partition) on SSD's, can we use the remaining space on that mirrored partition to extend my SQL 2014 buffer pool ? I understand that in this scenario, there is some competition for the I/O throughput between SQL Server's extended buffer pool and the OS. We intend to have the pagefile on a different disk, other than this specific SSD.Â
View 11 Replies View RelatedDear Friends,
I want your help to know the best way to cache the data of a dropdownbox returned by a SQL Query.(SELECT FIELD FROM DBO.TABLE)
This data returned by database is used in more than one dropdown on multiple pages. I want to cache only the dropdown control, not the entire page. Which is the best way to do it? The data isn't refreshed often, probably once per month.
Could you tell me the best way?
THANKS