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  • Geocaching - World wide treasure hunt

    I'm not quite sure how I came across this topic but actually I find it absolutely interesting, challenging and most of all a great fun for the family and friends. The interesting part is for sure that you can follow other peoples treasures and their preferred locations where a cache might be hidden. Of course, it wont be easy to find a cache after all. Sometimes there are even 'mystery caches' which have either riddles, further instructions or little brain games for you in order to find the actual cache - that's the challenge. And last but not least, those caches are hidden outdoor. A great experience to explore nature either on your own, or your family especially with children, or as a treasure hunting pack with a couple of friends. What is geocaching? It's a high-tech outdoor treasure hunting game that's a great way to explore the world with friends, family or on your own. Participants use GPS-enabled devices to locate hidden containers called geocaches. There are over one million geocaches hidden around the world today, waiting for you to find them. Visit Geocaching.com to search for geocaches near you.(Source: Referral Email of geocaching.com) Checkout the Geocaching 101 for further details and information. They also provide a video channel on YouTube. Which equipment do I need? Any GPS-enabled device is sufficient to go onto the hunt. I'm going to start our geocaching experience equipped with my Samsung Galaxy Tab. Additionally, I installed a geocaching.com client called c:geo that hopefully assists me soon. Combined with a map app like Google Maps and a nice Compass app you should be fully equipped and ready to go. I guess, that even a car navigation system is perfect for that task. Later on, with more experience and demand for technology (or precision) it might be interesting to opt-in for a pure GPS device, like a Garmin or any other brand on the market. {loadposition content_adsense} What is a geocache and what does it contain? In its simplest form, a cache always contains a logbook or logsheet for you to log your find. Larger caches may contain a logbook and any number of items. These items turn the adventure into a true treasure hunt. You never know what the cache owner or visitors to the cache may have left for you to enjoy. Remember, if you take something, leave something of equal or greater value in return. It is recommended that items in a cache be individually packaged in a clear, zipped plastic bag to protect them from the elements. Finding your first geocache Well, first you have to have interest to pick up the challenge. Then you have to check out the Geocache directory on geocaching.com. They have recommendations for beginner's caches but you are free to choose any. Actually, we have a Mystery Cache very close to our base, and I guess that we are going for that one on our first trip. Anyway, there is a very informative guide on the website which should answer all your questions about starting your new outdoor adventure. For sure, it's going to be rewarding. Team up with friends and family Especially as a beginner there might be misunderstandings in handling the GPS coordinates, the compass, or the map, and even finding the container at the documented position isn't easy in the first place. Luckily, there are logbook reports online from other hunters, and most of the time there are even 'spoiler' images available. But also bear in mind, that a geocache might have been removed or is lost due to unconscious people or whatever other reasons. Don't be disappointed in case that you can't find anything... There be nothing anymore. A general recommendation in this case would be to replace the missing container with a new one, and give feedback to the original owner about the state of that particular location. After all, it's about fun and active participation in a world-wide community. Geocaches in Mauritius? Yes, there are currently about 45 geocaches spread all over the island, and even a single in Rodriguez - that's gonna be a tough one. Hopefully, we will get increasing numbers as Geocaching.com allows, no better, even encourages you to hide new containers at your locations of choice. I think this is going to be real fun for us during the upcoming weeks and months. Especially, when we are travelling to other countries and transfer so-called trackable items between geocaches. On my first impression, Geocaching.com seems to be very mature, open and community-oriented. There are literally hundreds of thousands geocache 'hunters' all over the world. And usually finding a container remote from your home is very rewarding. I'll keep you updated in these matters during the next months to come...

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  • User Group Meeting Summary - April 2010

    - by Michael Stephenson
    Thanks to everyone who could make it to what turned out to be an excellent SBUG event.  First some thanks to:  Speakers: Anthony Ross and Elton Stoneman Host: The various people at Hitachi who helped to organise and arrange the venue.   Session 1 - Getting up and running with Windows Mobile and the Windows Azure Service Bus In this session Anthony discussed some considerations for using Windows Mobile and the Windows Azure Service Bus from a real-world project which Hitachi have been working on with EasyJet.  Anthony also walked through a simplified demo of the concepts which applied on the project.   In addition to the slides and demo it was also very interesting to discuss with the guys involved on this project to hear about their real experiences developing with the Azure Service Bus and some of the limitations they have had to work around in Windows Mobiles ability to interact with the service bus.   On the back of this session we will look to do some further activities around this topic and the guys offered to share their wish list of features for both Windows Mobile and Windows Azure which we will look to share for user group discussion.   Another interesting point was the cost aspects of using the ISB which were very low.   Session 2 - The Enterprise Cache In the second session Elton used a few slides which are based around one of his customer scenario's where they are looking into the concept of an Enterprise Cache within the organisation.  Elton discusses this concept and also a codeplex project he is putting together which allows you to take advantage of a cache with various providers such as Memcached, AppFabric Caching and Ncache.   Following the presentation it was interesting to hear peoples thoughts on various aspects such as the enterprise cache versus an out of process application cache.  Also there was interesting discussion around how people would like to search the cache in the future.   We will again look to put together some follow-up activity on this   Meeting Summary Following the meeting all slide decks are saved in the skydrive location where we keep content from all meetings: http://cid-40015ea59a1307c8.skydrive.live.com/browse.aspx/.Public/SBUG/SBUG%20Meetings/2010%20April   Remember that the details of all previous events are on the following page. http://uksoabpm.org/Events.aspx   Competition We had three copies of the Windows Identity Foundation Patterns and Practices book that were raffles on the night, it would be great to hear any feedback on the book from those who won it.   Recording The user group meeting was recorded and we will look to make this available online sometime soon.   UG Business The following things were discussed as general UG topics:   We will change the name of the user group to the UK Connected Systems User Group to we are more inline with other user groups who cover similar topics and we believe this will help us to attract more members.  The content or focus of the user group is not expected to change.   The next meeting is 26th May and can be registered at the following link: http://sbugmay2010.eventbrite.com/

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  • Operator of the week - Assert

    - by Fabiano Amorim
    Well my friends, I was wondering how to help you in a practical way to understand execution plans. So I think I'll talk about the Showplan Operators. Showplan Operators are used by the Query Optimizer (QO) to build the query plan in order to perform a specified operation. A query plan will consist of many physical operators. The Query Optimizer uses a simple language that represents each physical operation by an operator, and each operator is represented in the graphical execution plan by an icon. I'll try to talk about one operator every week, but so as to avoid having to continue to write about these operators for years, I'll mention only of those that are more common: The first being the Assert. The Assert is used to verify a certain condition, it validates a Constraint on every row to ensure that the condition was met. If, for example, our DDL includes a check constraint which specifies only two valid values for a column, the Assert will, for every row, validate the value passed to the column to ensure that input is consistent with the check constraint. Assert  and Check Constraints: Let's see where the SQL Server uses that information in practice. Take the following T-SQL: IF OBJECT_ID('Tab1') IS NOT NULL   DROP TABLE Tab1 GO CREATE TABLE Tab1(ID Integer, Gender CHAR(1))  GO  ALTER TABLE TAB1 ADD CONSTRAINT ck_Gender_M_F CHECK(Gender IN('M','F'))  GO INSERT INTO Tab1(ID, Gender) VALUES(1,'X') GO To the command above the SQL Server has generated the following execution plan: As we can see, the execution plan uses the Assert operator to check that the inserted value doesn't violate the Check Constraint. In this specific case, the Assert applies the rule, 'if the value is different to "F" and different to "M" than return 0 otherwise returns NULL'. The Assert operator is programmed to show an error if the returned value is not NULL; in other words, the returned value is not a "M" or "F". Assert checking Foreign Keys Now let's take a look at an example where the Assert is used to validate a foreign key constraint. Suppose we have this  query: ALTER TABLE Tab1 ADD ID_Genders INT GO  IF OBJECT_ID('Tab2') IS NOT NULL   DROP TABLE Tab2 GO CREATE TABLE Tab2(ID Integer PRIMARY KEY, Gender CHAR(1))  GO  INSERT INTO Tab2(ID, Gender) VALUES(1, 'F') INSERT INTO Tab2(ID, Gender) VALUES(2, 'M') INSERT INTO Tab2(ID, Gender) VALUES(3, 'N') GO  ALTER TABLE Tab1 ADD CONSTRAINT fk_Tab2 FOREIGN KEY (ID_Genders) REFERENCES Tab2(ID) GO  INSERT INTO Tab1(ID, ID_Genders, Gender) VALUES(1, 4, 'X') Let's look at the text execution plan to see what these Assert operators were doing. To see the text execution plan just execute SET SHOWPLAN_TEXT ON before run the insert command. |--Assert(WHERE:(CASE WHEN NOT [Pass1008] AND [Expr1007] IS NULL THEN (0) ELSE NULL END))      |--Nested Loops(Left Semi Join, PASSTHRU:([Tab1].[ID_Genders] IS NULL), OUTER REFERENCES:([Tab1].[ID_Genders]), DEFINE:([Expr1007] = [PROBE VALUE]))           |--Assert(WHERE:(CASE WHEN [Tab1].[Gender]<>'F' AND [Tab1].[Gender]<>'M' THEN (0) ELSE NULL END))           |    |--Clustered Index Insert(OBJECT:([Tab1].[PK]), SET:([Tab1].[ID] = RaiseIfNullInsert([@1]),[Tab1].[ID_Genders] = [@2],[Tab1].[Gender] = [Expr1003]), DEFINE:([Expr1003]=CONVERT_IMPLICIT(char(1),[@3],0)))           |--Clustered Index Seek(OBJECT:([Tab2].[PK]), SEEK:([Tab2].[ID]=[Tab1].[ID_Genders]) ORDERED FORWARD) Here we can see the Assert operator twice, first (looking down to up in the text plan and the right to left in the graphical plan) validating the Check Constraint. The same concept showed above is used, if the exit value is "0" than keep running the query, but if NULL is returned shows an exception. The second Assert is validating the result of the Tab1 and Tab2 join. It is interesting to see the "[Expr1007] IS NULL". To understand that you need to know what this Expr1007 is, look at the Probe Value (green text) in the text plan and you will see that it is the result of the join. If the value passed to the INSERT at the column ID_Gender exists in the table Tab2, then that probe will return the join value; otherwise it will return NULL. So the Assert is checking the value of the search at the Tab2; if the value that is passed to the INSERT is not found  then Assert will show one exception. If the value passed to the column ID_Genders is NULL than the SQL can't show a exception, in that case it returns "0" and keeps running the query. If you run the INSERT above, the SQL will show an exception because of the "X" value, but if you change the "X" to "F" and run again, it will show an exception because of the value "4". If you change the value "4" to NULL, 1, 2 or 3 the insert will be executed without any error. Assert checking a SubQuery: The Assert operator is also used to check one subquery. As we know, one scalar subquery can't validly return more than one value: Sometimes, however, a  mistake happens, and a subquery attempts to return more than one value . Here the Assert comes into play by validating the condition that a scalar subquery returns just one value. Take the following query: INSERT INTO Tab1(ID_TipoSexo, Sexo) VALUES((SELECT ID_TipoSexo FROM Tab1), 'F')    INSERT INTO Tab1(ID_TipoSexo, Sexo) VALUES((SELECT ID_TipoSexo FROM Tab1), 'F')    |--Assert(WHERE:(CASE WHEN NOT [Pass1016] AND [Expr1015] IS NULL THEN (0) ELSE NULL END))        |--Nested Loops(Left Semi Join, PASSTHRU:([tempdb].[dbo].[Tab1].[ID_TipoSexo] IS NULL), OUTER REFERENCES:([tempdb].[dbo].[Tab1].[ID_TipoSexo]), DEFINE:([Expr1015] = [PROBE VALUE]))              |--Assert(WHERE:([Expr1017]))             |    |--Compute Scalar(DEFINE:([Expr1017]=CASE WHEN [tempdb].[dbo].[Tab1].[Sexo]<>'F' AND [tempdb].[dbo].[Tab1].[Sexo]<>'M' THEN (0) ELSE NULL END))              |         |--Clustered Index Insert(OBJECT:([tempdb].[dbo].[Tab1].[PK__Tab1__3214EC277097A3C8]), SET:([tempdb].[dbo].[Tab1].[ID_TipoSexo] = [Expr1008],[tempdb].[dbo].[Tab1].[Sexo] = [Expr1009],[tempdb].[dbo].[Tab1].[ID] = [Expr1003]))              |              |--Top(TOP EXPRESSION:((1)))              |                   |--Compute Scalar(DEFINE:([Expr1008]=[Expr1014], [Expr1009]='F'))              |                        |--Nested Loops(Left Outer Join)              |                             |--Compute Scalar(DEFINE:([Expr1003]=getidentity((1856985942),(2),NULL)))              |                             |    |--Constant Scan              |                             |--Assert(WHERE:(CASE WHEN [Expr1013]>(1) THEN (0) ELSE NULL END))              |                                  |--Stream Aggregate(DEFINE:([Expr1013]=Count(*), [Expr1014]=ANY([tempdb].[dbo].[Tab1].[ID_TipoSexo])))             |                                       |--Clustered Index Scan(OBJECT:([tempdb].[dbo].[Tab1].[PK__Tab1__3214EC277097A3C8]))              |--Clustered Index Seek(OBJECT:([tempdb].[dbo].[Tab2].[PK__Tab2__3214EC27755C58E5]), SEEK:([tempdb].[dbo].[Tab2].[ID]=[tempdb].[dbo].[Tab1].[ID_TipoSexo]) ORDERED FORWARD)  You can see from this text showplan that SQL Server as generated a Stream Aggregate to count how many rows the SubQuery will return, This value is then passed to the Assert which then does its job by checking its validity. Is very interesting to see that  the Query Optimizer is smart enough be able to avoid using assert operators when they are not necessary. For instance: INSERT INTO Tab1(ID_TipoSexo, Sexo) VALUES((SELECT ID_TipoSexo FROM Tab1 WHERE ID = 1), 'F') INSERT INTO Tab1(ID_TipoSexo, Sexo) VALUES((SELECT TOP 1 ID_TipoSexo FROM Tab1), 'F')  For both these INSERTs, the Query Optimiser is smart enough to know that only one row will ever be returned, so there is no need to use the Assert. Well, that's all folks, I see you next week with more "Operators". Cheers, Fabiano

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  • DBCC MEMUSAGE in 2005/8 ?

    - by steveh99999
    I used to like using undocumented command DBCC MEMUSAGE in SQL 2000 to see which tables were using space in SQL data cache. In SQL 2005, this command is not longer present. Instead a DMV – sys.dm_os_buffer_descriptors – can be used to display data cache contents,  but this doesn’t quite give you the same output as DBCC MEMUSAGE. I’m also aware that you can use Quest’s spotlight tool to view a summary of data cache contents. Using  this post by Umachandar Jayachandran  of Microsoft, I was able to create the following equivalent for SQL 2005/8. I’ve wrapped Umachandar’s original query in a CTE to produce summary information :- ;WITH memusage_CTE AS (SELECT bd.database_id, bd.file_id, bd.page_id, bd.page_type , COALESCE(p1.object_id, p2.object_id) AS object_id , COALESCE(p1.index_id, p2.index_id) AS index_id , bd.row_count, bd.free_space_in_bytes, CONVERT(TINYINT,bd.is_modified) AS 'DirtyPage' FROM sys.dm_os_buffer_descriptors AS bd JOIN sys.allocation_units AS au ON au.allocation_unit_id = bd.allocation_unit_id OUTER APPLY ( SELECT TOP(1) p.object_id, p.index_id FROM sys.partitions AS p WHERE p.hobt_id = au.container_id AND au.type IN (1, 3) ) AS p1 OUTER APPLY ( SELECT TOP(1) p.object_id, p.index_id FROM sys.partitions AS p WHERE p.partition_id = au.container_id AND au.type = 2 ) AS p2 WHERE  bd.database_id = DB_ID() AND bd.page_type IN ('DATA_PAGE', 'INDEX_PAGE') ) SELECT TOP 20 DB_NAME(database_id) AS 'Database',OBJECT_NAME(object_id,database_id) AS 'Table Name', index_id,COUNT(*) AS 'Pages in Cache', SUM(dirtyPage) AS 'Dirty Pages' FROM memusage_CTE GROUP BY database_id, object_id, index_id ORDER BY COUNT(*) DESC I’m not 100% happy with the results of the above query however… I’ve noticed that on a busy BizTalk messageBox database  it will return information on pages that contain GHOST rows – . ie where data has already been deleted but has yet to be cleaned-up by a background process – I’m need to investigate further why cache on this server apparently contains so much GHOST data… For more information on the background ghost cleanup process, see this article by Paul Randall. However, I think the results of this query should still be of interest to a DBA. I have another post to come shortly regarding an example I encountered where this information proved useful to me… I notice in SQL 2008, sys.dm_os_buffer_descriptors gained an extra column – numa_mode – I’m interested to see how this is populated and how useful this column can be on a NUMA-enabled system. I’m assuming in theory you could use this column to help analyse how your tables are spread across Numa-enabled data-cache ?

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  • SPARC M7 Chip - 32 cores - Mind Blowing performance

    - by Angelo-Oracle
    The M7 Chip Oracle just announced its Next Generation Processor at the HotChips HC26 conference. As the Tech Lead in our Systems Division's Partner group, I had a front row seat to the extraordinary price performance advantage of Oracle current T5 and M6 based systems. Partner after partner tested  these systems and were impressed with it performance. Just read some of the quotes to see what our partner has been saying about our hardware. We just announced our next generation processor, the M7. This has 32 cores (up from 16-cores in T5 and 12-cores in M6). With 20 nm technology  this is our most advanced processor. The processor has more cores than anything else in the industry today. After the Sun acquisition Oracle has released 5 processors in 4 years and this is the 6th.  The S4 core  The M7 is built using the foundation of the S4 core. This is the next generation core technology. Like its predecessor, the S4 has 8 dynamic threads. It increases the frequency while maintaining the Pipeline depth. Each core has its own fine grain power estimator that keeps the core within its power envelop in 250 nano-sec granularity. Each core also includes Software in Silicon features for Application Acceleration Support. Each core includes features to improve Application Data Integrity, with almost no performance loss. The core also allows using part of the Virtual Address to store meta-data.  User-Level Synchronization Instructions are also part of the S4 core. Each core has 16 KB Instruction and 16 KB Data L1 cache. The Core Clusters  The cores on the M7 chip are organized in sets of 4-core clusters. The core clusters share  L2 cache.  All four cores in the complex share 256 KB of 4 way set associative L2 Instruction Cache, with over 1/2 TB/s of throughput. Two cores share 256 KB of 8 way set associative L2 Data Cache, with over 1/2 TB/s of throughput. With this innovative Core Cluster architecture, the M7 doubles core execution bandwidth. to maximize per-thread performance.  The Chip  Each  M7 chip has 8 sets of these core-clusters. The chip has 64 MB on-chip L3 cache. This L3 caches is shared among all the cores and is partitioned into 8 x 8 MB chunks. Each chunk is  8-way set associative cache. The aggregate bandwidth for the L3 cache on the chip is over 1.6TB/s. Each chip has 4 DDR4 memory controllers and can support upto 16 DDR4 DIMMs, allowing for 2 TB of RAM/chip. The chip also includes 4 internal links of PCIe Gen3 I/O controllers.  Each chip has 7 coherence links, allowing for 8 of these chips to be connected together gluelessly. Also 32 of these chips can be connected in an SMP configuration. A potential system with 32 chips will have 1024 cores and 8192 threads and 64 TB of RAM.  Software in Silicon The M7 chip has many built in Application Accelerators in Silicon. These features will be exposed to our Software partners using the SPARC Accelerator Program.  The M7  has built-in logic to decompress data at the speed of memory access. This means that applications can directly work on compressed data in memory increasing the data access rates. The VA Masking feature allows the use of part of the virtual address to store meta-data.  Realtime Application Data Integrity The Realtime Application Data Integrity feature helps applications safeguard against invalid, stale memory reference and buffer overflows. The first 4-bits if the Pointer can be used to store a version number and this version number is also maintained in the memory & cache lines. When a pointer accesses memory the hardware checks to make sure the two versions match. A SEGV signal is raised when there is a mismatch. This feature can be used by the Database, applications and the OS.  M7 Database In-Memory Query Accelerator The M7 chip also includes a In-Silicon Query Engines.  These accelerate tasks that work on In-Memory Columnar Vectors. Oracle In-Memory options stores data in Column Format. The M7 Query Engine can speed up In-Memory Format Conversion, Value and Range Comparisons and Set Membership lookups. This engine can work on Compressed data - this means not only are we accelerating the query performance but also increasing the memory bandwidth for queries.  SPARC Accelerated Program  At the Hotchips conference we also introduced the SPARC Accelerated Program to provide our partners and third part developers access to all the goodness of the M7's SPARC Application Acceleration features. Please get in touch with us if you are interested in knowing more about this program. 

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  • Windows Azure: Caching

    - by xamlnotes
    I was poking around today and found this great article on caching: http://www.cloudcomputingdevelopment.net/cache-management-with-windows-azure/ Caching is a great way to boost application performance and keep down overhead on a database or file system. Its also great when you have say 3 web roles as shown in this articles Figure 2 that can share the same cache. If one of the roles goes offline then the cache is still there and can be used. You can change out your asp.net caching to use this pretty easy. Its pretty cool. There’s a sample that’s mentioned in the article that shows how to use this. You can download the cache here.

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  • A quick look at: sys.dm_os_buffer_descriptors

    - by Jonathan Allen
    SQL Server places data into cache as it reads it from disk so as to speed up future queries. This dmv lets you see how much data is cached at any given time and knowing how this changes over time can help you ensure your servers run smoothly and are adequately resourced to run your systems. This dmv gives the number of cached pages in the buffer pool along with the database id that they relate to: USE [tempdb] GO SELECT COUNT(*) AS cached_pages_count , CASE database_id WHEN 32767 THEN 'ResourceDb' ELSE DB_NAME(database_id) END AS Database_name FROM sys.dm_os_buffer_descriptors GROUP BY DB_NAME(database_id) , database_id ORDER BY cached_pages_count DESC; This gives you results which are quite useful, but if you add a new column with the code: …to convert the pages value to show a MB value then they become more relevant and meaningful. To see how your server reacts to queries, start up SSMS and connect to a test server and database – mine is called AdventureWorks2008. Make sure you start from a know position by running: -- Only run this on a test server otherwise your production server's-- performance may drop off a cliff and your phone will start ringing. DBCC DROPCLEANBUFFERS GO Now we can run a query that would normally turn a DBA’s hair white: USE [AdventureWorks2008] go SELECT * FROM [Sales].[SalesOrderDetail] AS sod INNER JOIN [Sales].[SalesOrderHeader] AS soh ON [sod].[SalesOrderID] = [soh].[SalesOrderID] …and then check our cache situation: A nice low figure – not! Almost 2000 pages of data in cache equating to approximately 15MB. Luckily these tables are quite narrow; if this had been on a table with more columns then this could be even more dramatic. So, let’s make our query more efficient. After resetting the cache with the DROPCLEANBUFFERS and FREEPROCCACHE code above, we’ll only select the columns we want and implement a WHERE predicate to limit the rows to a specific customer. SELECT [sod].[OrderQty] , [sod].[ProductID] , [soh].[OrderDate] , [soh].[CustomerID] FROM [Sales].[SalesOrderDetail] AS sod INNER JOIN [Sales].[SalesOrderHeader] AS soh ON [sod].[SalesOrderID] = [soh].[SalesOrderID] WHERE [soh].[CustomerID] = 29722 …and check our effect cache: Now that is more sympathetic to our server and the other systems sharing its resources. I can hear you asking: “What has this got to do with logging, Jonathan?” Well, a smart DBA will keep an eye on this metric on their servers so they know how their hardware is coping and be ready to investigate anomalies so that no ‘disruptive’ code starts to unsettle things. Capturing this information over a period of time can lead you to build a picture of how a database relies on the cache and how it interacts with other databases. This might allow you to decide on appropriate schedules for over night jobs or otherwise balance the work of your server. You could schedule this job to run with a SQL Agent job and store the data in your DBA’s database by creating a table with: IF OBJECT_ID('CachedPages') IS NOT NULL DROP TABLE CachedPages CREATE TABLE CachedPages ( cached_pages_count INT , MB INT , Database_Name VARCHAR(256) , CollectedOn DATETIME DEFAULT GETDATE() ) …and then filling it with: INSERT INTO [dbo].[CachedPages] ( [cached_pages_count] , [MB] , [Database_Name] ) SELECT COUNT(*) AS cached_pages_count , ( COUNT(*) * 8.0 ) / 1024 AS MB , CASE database_id WHEN 32767 THEN 'ResourceDb' ELSE DB_NAME(database_id) END AS Database_name FROM sys.dm_os_buffer_descriptors GROUP BY database_id After this has been left logging your system metrics for a while you can easily see how your databases use the cache over time and may see some spikes that warrant your attention. This sort of logging can be applied to all sorts of server statistics so that you can gather information that will give you baseline data on how your servers are performing. This means that when you get a problem you can see what statistics are out of their normal range and target you efforts to resolve the issue more rapidly.

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  • Page output caching for dynamic web applications

    - by Mike Ellis
    I am currently working on a web application where the user steps (forward or back) through a series of pages with "Next" and "Previous" buttons, entering data until they reach a page with the "Finish" button. Until finished, all data is stored in Session state, then sent to the mainframe database via web services at the end of the process. Some of the pages display data from previous pages in order to collect additional information. These pages can never be cached because they are different for every user. For pages that don't display this dynamic data, they can be cached, but only the first time they load. After that, the data that was previously entered needs to be displayed. This requires Page_Load to fire, which means the page can't be cached at that point. A couple of weeks ago, I knew almost nothing about implementing page caching. Now I still don't know much, but I know a little bit, and here is the solution that I developed with the help of others on my team and a lot of reading and trial-and-error. We have a base page class defined from which all pages inherit. In this class I have defined a method that sets the caching settings programmatically. For pages that can be cached, they call this base page method in their Page_Load event within a if(!IsPostBack) block, which ensures that only the page itself gets cached, not the data on the page. if(!IsPostBack) {     ...     SetCacheSettings();     ... } protected void SetCacheSettings() {     Response.Cache.AddValidationCallback(new HttpCacheValidateHandler(Validate), null);     Response.Cache.SetExpires(DateTime.Now.AddHours(1));     Response.Cache.SetSlidingExpiration(true);     Response.Cache.SetValidUntilExpires(true);     Response.Cache.SetCacheability(HttpCacheability.ServerAndNoCache); } The AddValidationCallback sets up an HttpCacheValidateHandler method called Validate which runs logic when a cached page is requested. The Validate method signature is standard for this method type. public static void Validate(HttpContext context, Object data, ref HttpValidationStatus status) {     string visited = context.Request.QueryString["v"];     if (visited != null && "1".Equals(visited))     {         status = HttpValidationStatus.IgnoreThisRequest; //force a page load     }     else     {         status = HttpValidationStatus.Valid; //load from cache     } } I am using the HttpValidationStatus values IgnoreThisRequest or Valid which forces the Page_Load event method to run or allows the page to load from cache, respectively. Which one is set depends on the value in the querystring. The value in the querystring is set up on each page in the "Next" and "Previous" button click event methods based on whether the page that the button click is taking the user to has any data on it or not. bool hasData = HasPageBeenVisited(url); if (hasData) {     url += VISITED; } Response.Redirect(url); The HasPageBeenVisited method determines whether the destination page has any data on it by checking one of its required data fields. (I won't include it here because it is very system-dependent.) VISITED is a string constant containing "?v=1" and gets appended to the url if the destination page has been visited. The reason this logic is within the "Next" and "Previous" button click event methods is because 1) the Validate method is static which doesn't allow it to access non-static data such as the data fields for a particular page, and 2) at the time at which the Validate method runs, either the data has not yet been deserialized from Session state or is not available (different AppDomain?) because anytime I accessed the Session state information from the Validate method, it was always empty.

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  • hosting environment for delivering FLVs

    - by Gotys
    What would be the ideal hardware setup for pushing lots of bandwith on a tube site? We have ever-expanding cloud storage where users upload the movies, then we have these web-delivery machines which cache the FLV files on its local harddrives and deliver them to users. Each cache machine can deliver 1200 mbits/s , if it has SAS 8 harddrives. Such a cache machine costs us $550/month for 8x160gb -- so each machine can cache only 160GB at any given time. If we want to cache more then 160gb , we need to add another machine..another $550/month..etc. This is very un-economical so I am wondering if we have any experts here who can figure out a better setup. I've been looking into "gluster FS", but I am not sure if this thing can push a lot of bandwith. Any ideas highly appreciated. Thank you!

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  • Installing 12.04 within 11.04

    - by user288752
    I recently installed 11.04 from an installation disk (overwriting Windows in the process). I know 11.04 is no longer supported but I had no problems subsequently upgrading it to 12.04 (via 11.10) a couple of months ago on another device. This time though, things are different. I can't upgrade through update manager because Ubuntu then tells me I have no internet connection, which is (obviously incorrect). I have tried to circumvent the problem by downloading the 12:04 iso from ubuntu.com directly but now I'm troubled by something else. The download is succesfull but after mounting the iso I can't interact with it. When I try to access the Wubi it gives me the following message: Archive: /home/lars/.cache/.fr-7g75Fe/wubi.exe [/home/lars/.cache/.fr-7g75Fe/wubi.exe] End-of-central-directory signature not found. Either this file is not a zipfile, or it constitutes one disk of a multi-part archive. In the latter case the central directory and zipfile comment will be found on the last disk(s) of this archive. zipinfo: cannot find zipfile directory in one of /home/lars/.cache/.fr-7g75Fe/wubi.exe or /home/lars/.cache/.fr-7g75Fe/wubi.exe.zip, and cannot find /home/lars/.cache/.fr-7g75Fe/wubi.exe.ZIP, period. What am I doing wrong here?

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  • Fixing Chrome&rsquo;s AJAX Request Caching Bug

    - by Steve Wilkes
    I recently had to make a set of web pages restore their state when the user arrived on them after clicking the browser’s back button. The pages in question had various content loaded in response to user actions, which meant I had to manually get them back into a valid state after the page loaded. I got hold of the page’s data in a JavaScript ViewModel using a JQuery ajax call, then iterated over the properties, filling in the fields as I went. I built in the ability to describe dependencies between inputs to make sure fields were filled in in the correct order and at the correct time, and that all worked nicely. To make sure the browser didn’t cache the AJAX call results I used the JQuery’s cache: false option, and ASP.NET MVC’s OutputCache attribute for good measure. That all worked perfectly… except in Chrome. Chrome insisted on retrieving the data from its cache. cache: false adds a random query string parameter to make the browser think it’s a unique request – it made no difference. I made the AJAX call a POST – it made no difference. Eventually what I had to do was add a random token to the URL (not the query string) and use MVC routing to deliver the request to the correct action. The project had a single Controller for all AJAX requests, so this route: routes.MapRoute( name: "NonCachedAjaxActions", url: "AjaxCalls/{cacheDisablingToken}/{action}", defaults: new { controller = "AjaxCalls" }, constraints: new { cacheDisablingToken = "[0-9]+" }); …and this amendment to the ajax call: function loadPageData(url) { // Insert a timestamp before the URL's action segment: var indexOfFinalUrlSeparator = url.lastIndexOf("/"); var uniqueUrl = url.substring(0, indexOfFinalUrlSeparator) + new Date().getTime() + "/" + url.substring(indexOfFinalUrlSeparator); // Call the now-unique action URL: $.ajax(uniqueUrl, { cache: false, success: completePageDataLoad }); } …did the trick.

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  • Why did Ubuntu suddenly get so slow?

    - by user101383
    12.10 has been slowing down mysteriously. Normally, in past versions, I can log in, open Firefox, and it will pop up within seconds. 12.10 is like that upon install too, though once I install my old apps, it gets very slow by Ubuntu standards. After login the hard drive will just make noise for a while before the OS will do anything. Hardware: enter description: Desktop Computer product: XPS 8300 () vendor: Dell Inc. serial: B6G2WR1 width: 64 bits capabilities: smbios-2.6 dmi-2.6 vsyscall32 configuration: boot=normal chassis=desktop uuid=44454C4C-3600-1047-8032-C2C04F575231 core description: Motherboard product: 0Y2MRG vendor: Dell Inc. physical id: 0 version: A00 serial: ..CN7360419G04VQ. slot: To Be Filled By O.E.M. *cpu description: CPU product: Intel(R) Core(TM) i7-2600 CPU @ 3.40GHz vendor: Intel Corp. physical id: 4 bus info: cpu@0 version: Intel(R) Core(TM) i7-2600 CPU @ 3.40GHz serial: To Be Filled By O.E.M. slot: CPU 1 size: 1600MHz capacity: 1600MHz width: 64 bits clock: 100MHz capabilities: x86-64 fpu fpu_exception wp vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx rdtscp constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic popcnt tsc_deadline_timer aes xsave avx lahf_lm ida arat epb xsaveopt pln pts dtherm tpr_shadow vnmi flexpriority ept vpid cpufreq configuration: cores=4 enabledcores=1 threads=2 *-cache:0 description: L1 cache physical id: 5 slot: L1-Cache size: 256KiB capacity: 256KiB capabilities: internal write-through unified *-cache:1 description: L2 cache physical id: 6 slot: L2-Cache size: 1MiB capacity: 1MiB capabilities: internal write-through unified *-cache:2 DISABLED description: L3 cache physical id: 7 slot: L3-Cache size: 8MiB capacity: 8MiB capabilities: internal write-back unified *-memory description: System Memory physical id: 20 slot: System board or motherboard size: 8GiB *-bank:0 description: SODIMM DDR3 Synchronous 1333 MHz (0.8 ns) product: NT2GC64B88B0NF-CG vendor: Nanya physical id: 0 serial: 7228183 slot: DIMM3 size: 2GiB width: 64 bits clock: 1333MHz (0.8ns) *-bank:1 description: SODIMM DDR3 Synchronous 1333 MHz (0.8 ns) product: NT2GC64B88B0NF-CG vendor: Nanya physical id: 1 serial: 1E28183 slot: DIMM1 size: 2GiB width: 64 bits clock: 1333MHz (0.8ns) *-bank:2 description: SODIMM DDR3 Synchronous 1333 MHz (0.8 ns) product: NT2GC64B88B0NF-CG vendor: Nanya physical id: 2 serial: 9E28183 slot: DIMM4 size: 2GiB width: 64 bits clock: 1333MHz (0.8ns) *-bank:3 description: SODIMM DDR3 Synchronous 1333 MHz (0.8 ns) product: NT2GC64B88B0NF-CG vendor: Nanya physical id: 3 serial: 5527183 slot: DIMM2 size: 2GiB width: 64 bits clock: 1333MHz (0.8ns) *-firmware description: BIOS vendor: Dell Inc. physical id: 0 version: A05 date: 09/21/2011 size: 64KiB capacity: 4032KiB capabilities: mca pci upgrade shadowing escd cdboot bootselect socketedrom edd int13floppy1200 int13floppy720 int13floppy2880 int5printscreen int9keyboard int14serial int17printer int10video acpi usb zipboot biosbootspecification *-pci description: Host bridge product: 2nd Generation Core Processor Family DRAM Controller vendor: Intel Corporation physical id: 100 bus info: pci@0000:00:00.0 version: 09 width: 32 bits clock: 33MHz *-pci:0 description: PCI bridge product: Xeon E3-1200/2nd Generation Core Processor Family PCI Express Root Port vendor: Intel Corporation physical id: 1 bus info: pci@0000:00:01.0 version: 09 width: 32 bits clock: 33MHz capabilities: pci pm msi pciexpress normal_decode bus_master cap_list configuration: driver=pcieport resources: irq:40 ioport:e000(size=4096) memory:fe600000-fe6fffff ioport:d0000000(size=268435456) *-display description: VGA compatible controller product: Juniper [Radeon HD 5700 Series] vendor: Advanced Micro Devices [AMD] nee ATI physical id: 0 bus info: pci@0000:01:00.0 version: 00 width: 64 bits clock: 33MHz capabilities: pm pciexpress msi vga_controller bus_master cap_list rom configuration: driver=radeon latency=0 resources: irq:44 memory:d0000000-dfffffff memory:fe620000-fe63ffff ioport:e000(size=256) memory:fe600000-fe61ffff *-multimedia description: Audio device product: Juniper HDMI Audio [Radeon HD 5700 Series] vendor: Advanced Micro Devices [AMD] nee ATI physical id: 0.1 bus info: pci@0000:01:00.1 version: 00 width: 64 bits clock: 33MHz capabilities: pm pciexpress msi bus_master cap_list configuration: driver=snd_hda_intel latency=0 resources: irq:48 memory:fe640000-fe643fff *-communication description: Communication controller product: 6 Series/C200 Series Chipset Family MEI Controller #1 vendor: Intel Corporation physical id: 16 bus info: pci@0000:00:16.0 version: 04 width: 64 bits clock: 33MHz capabilities: pm msi bus_master cap_list configuration: driver=mei latency=0 resources: irq:45 memory:fe708000-fe70800f *-usb:0 description: USB controller product: 6 Series/C200 Series Chipset Family USB Enhanced Host Controller #2 vendor: Intel Corporation physical id: 1a bus info: pci@0000:00:1a.0 version: 05 width: 32 bits clock: 33MHz capabilities: pm debug ehci bus_master cap_list configuration: driver=ehci_hcd latency=0 resources: irq:16 memory:fe707000-fe7073ff *-multimedia description: Audio device product: 6 Series/C200 Series Chipset Family High Definition Audio Controller vendor: Intel Corporation physical id: 1b bus info: pci@0000:00:1b.0 version: 05 width: 64 bits clock: 33MHz capabilities: pm msi pciexpress bus_master cap_list configuration: driver=snd_hda_intel latency=0 resources: irq:46 memory:fe700000-fe703fff *-pci:1 description: PCI bridge product: 6 Series/C200 Series Chipset Family PCI Express Root Port 1 vendor: Intel Corporation physical id: 1c bus info: pci@0000:00:1c.0 version: b5 width: 32 bits clock: 33MHz capabilities: pci pciexpress msi pm normal_decode bus_master cap_list configuration: driver=pcieport resources: irq:41 memory:fe500000-fe5fffff *-network description: Network controller product: BCM4313 802.11b/g/n Wireless LAN Controller vendor: Broadcom Corporation physical id: 0 bus info: pci@0000:02:00.0 version: 01 width: 64 bits clock: 33MHz capabilities: pm msi pciexpress bus_master cap_list configuration: driver=bcma-pci-bridge latency=0 resources: irq:16 memory:fe500000-fe503fff *-pci:2 description: PCI bridge product: 6 Series/C200 Series Chipset Family PCI Express Root Port 4 vendor: Intel Corporation physical id: 1c.3 bus info: pci@0000:00:1c.3 version: b5 width: 32 bits clock: 33MHz capabilities: pci pciexpress msi pm normal_decode bus_master cap_list configuration: driver=pcieport resources: irq:42 memory:fe400000-fe4fffff *-network description: Ethernet interface product: NetLink BCM57788 Gigabit Ethernet PCIe vendor: Broadcom Corporation physical id: 0 bus info: pci@0000:03:00.0 logical name: eth0 version: 01 serial: 18:03:73:e1:a7:71 size: 100Mbit/s capacity: 1Gbit/s width: 64 bits clock: 33MHz capabilities: pm msi pciexpress bus_master cap_list ethernet physical tp mii 10bt 10bt-fd 100bt 100bt-fd 1000bt 1000bt-fd autonegotiation configuration: autonegotiation=on broadcast=yes driver=tg3 driverversion=3.123 duplex=full firmware=sb ip=192.168.1.3 latency=0 link=yes multicast=yes port=MII speed=100Mbit/s resources: irq:47 memory:fe400000-fe40ffff *-usb:1 description: USB controller product: 6 Series/C200 Series Chipset Family USB Enhanced Host Controller #1 vendor: Intel Corporation physical id: 1d bus info: pci@0000:00:1d.0 version: 05 width: 32 bits clock: 33MHz capabilities: pm debug ehci bus_master cap_list configuration: driver=ehci_hcd latency=0 resources: irq:23 memory:fe706000-fe7063ff *-isa description: ISA bridge product: H67 Express Chipset Family LPC Controller vendor: Intel Corporation physical id: 1f bus info: pci@0000:00:1f.0 version: 05 width: 32 bits clock: 33MHz capabilities: isa bus_master cap_list configuration: latency=0 *-storage description: SATA controller product: 6 Series/C200 Series Chipset Family SATA AHCI Controller vendor: Intel Corporation physical id: 1f.2 bus info: pci@0000:00:1f.2 version: 05 width: 32 bits clock: 66MHz capabilities: storage msi pm ahci_1.0 bus_master cap_list configuration: driver=ahci latency=0 resources: irq:43 ioport:f070(size=8) ioport:f060(size=4) ioport:f050(size=8) ioport:f040(size=4) ioport:f020(size=32) memory:fe705000-fe7057ff *-serial UNCLAIMED description: SMBus product: 6 Series/C200 Series Chipset Family SMBus Controller vendor: Intel Corporation physical id: 1f.3 bus info: pci@0000:00:1f.3 version: 05 width: 64 bits clock: 33MHz configuration: latency=0 resources: memory:fe704000-fe7040ff ioport:f000(size=32) *-scsi:0 physical id: 1 logical name: scsi0 capabilities: emulated *-disk description: ATA Disk product: Hitachi HUA72201 vendor: Hitachi physical id: 0.0.0 bus info: scsi@0:0.0.0 logical name: /dev/sda version: JP4O serial: JPW9J0HD21BTZC size: 931GiB (1TB) capabilities: partitioned partitioned:dos configuration: ansiversion=5 sectorsize=512 signature=000641dc *-volume:0 description: EXT4 volume vendor: Linux physical id: 1 bus info: scsi@0:0.0.0,1 logical name: /dev/sda1 logical name: / version: 1.0 serial: 4e3d91b7-fd38-4f44-a9e9-ba3c39b926ec size: 585GiB capacity: 585GiB capabilities: primary journaled extended_attributes large_files huge_files dir_nlink recover extents ext4 ext2 initialized configuration: created=2012-10-21 16:26:50 filesystem=ext4 lastmountpoint=/ modified=2012-10-29 18:12:08 mount.fstype=ext4 mount.options=rw,relatime,errors=remount-ro,data=ordered mounted=2012-10-29 18:12:08 state=mounted *-volume:1 description: Extended partition physical id: 2 bus info: scsi@0:0.0.0,2 logical name: /dev/sda2 size: 7823MiB capacity: 7823MiB capabilities: primary extended partitioned partitioned:extended *-logicalvolume description: Linux swap / Solaris partition physical id: 5 logical name: /dev/sda5 capacity: 7823MiB capabilities: nofs *-volume:2 description: Windows NTFS volume physical id: 3 bus info: scsi@0:0.0.0,3 logical name: /dev/sda3 version: 3.1 serial: 84a92aae-347b-7940-a2d1-f4745b885ef2 size: 337GiB capacity: 337GiB capabilities: primary bootable ntfs initialized configuration: clustersize=4096 created=2012-10-21 18:43:39 filesystem=ntfs modified_by_chkdsk=true mounted_on_nt4=true resize_log_file=true state=dirty upgrade_on_mount=true *-scsi:1 physical id: 2 logical name: scsi1 capabilities: emulated *-cdrom description: DVD-RAM writer product: DVDRWBD DH-12E3S vendor: PLDS physical id: 0.0.0 bus info: scsi@1:0.0.0 logical name: /dev/cdrom logical name: /dev/cdrw logical name: /dev/dvd logical name: /dev/dvdrw logical name: /dev/sr0 version: MD11 capabilities: removable audio cd-r cd-rw dvd dvd-r dvd-ram configuration: ansiversion=5 status=nodisc *-scsi:2 physical id: 3 bus info: usb@2:1.8 logical name: scsi6 capabilities: emulated scsi-host configuration: driver=usb-storage *-disk:0 description: SCSI Disk physical id: 0.0.0 bus info: scsi@6:0.0.0 logical name: /dev/sdb configuration: sectorsize=512 *-disk:1 description: SCSI Disk physical id: 0.0.1 bus info: scsi@6:0.0.1 logical name: /dev/sdc configuration: sectorsize=512 *-disk:2 description: SCSI Disk physical id: 0.0.2 bus info: scsi@6:0.0.2 logical name: /dev/sdd configuration: sectorsize=512 *-disk:3 description: SCSI Disk product: MS/MS-Pro vendor: Generic- physical id: 0.0.3 bus info: scsi@6:0.0.3 logical name: /dev/sde version: 1.03 serial: 3 capabilities: removable configuration: sectorsize=512 *-medium physical id: 0 logical name: /dev/sde

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  • How to determine if a package is a meta-package from the command line?

    - by cirosantilli
    How can I determine if a package is a meta-package from the command line, possibly via apt-get, aptitude or apt-cache? I have tried: apt-cache show texlive-full apt-cache showpkg texlive-full but the only way I can tell this package is meta is by reading the "en-description" field. Is there a more automatic way of doing this, that will give me a yes/no response, or at least have a field such as then "en-description" dedicated to this?

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  • PASS Summit 2011 &ndash; Part III

    - by Tara Kizer
    Well we’re about a month past PASS Summit 2011, and yet I haven’t finished blogging my notes! Between work and home life, I haven’t been able to come up for air in a bit.  Now on to my notes… On Thursday of the PASS Summit 2011, I attended Klaus Aschenbrenner’s (blog|twitter) “Advanced SQL Server 2008 Troubleshooting”, Joe Webb’s (blog|twitter) “SQL Server Locking & Blocking Made Simple”, Kalen Delaney’s (blog|twitter) “What Happened? Exploring the Plan Cache”, and Paul Randal’s (blog|twitter) “More DBA Mythbusters”.  I think my head grew two times in size from the Thursday sessions.  Just WOW! I took a ton of notes in Klaus' session.  He took a deep dive into how to troubleshoot performance problems.  Here is how he goes about solving a performance problem: Start by checking the wait stats DMV System health Memory issues I/O issues I normally start with blocking and then hit the wait stats.  Here’s the wait stat query (Paul Randal’s) that I use when working on a performance problem.  He highlighted a few waits to be aware of such as WRITELOG (indicates IO subsystem problem), SOS_SCHEDULER_YIELD (indicates CPU problem), and PAGEIOLATCH_XX (indicates an IO subsystem problem or a buffer pool problem).  Regarding memory issues, Klaus recommended that as a bare minimum, one should set the “max server memory (MB)” in sp_configure to 2GB or 10% reserved for the OS (whichever comes first).  This is just a starting point though! Regarding I/O issues, Klaus talked about disk partition alignment, which can improve SQL I/O performance by up to 100%.  You should use 64kb for NTFS cluster, and it’s automatic in Windows 2008 R2. Joe’s locking and blocking presentation was a good session to really clear up the fog in my mind about locking.  One takeaway that I had no idea could be done was that you can set a timeout in T-SQL code view LOCK_TIMEOUT.  If you do this via the application, you should trap error 1222. Kalen’s session went into execution plans.  The minimum size of a plan is 24k.  This adds up fast especially if you have a lot of plans that don’t get reused much.  You can use sys.dm_exec_cached_plans to check how often a plan is being reused by checking the usecounts column.  She said that we can use DBCC FLUSHPROCINDB to clear out the stored procedure cache for a specific database.  I didn’t know we had this available, so this was great to hear.  This will be less intrusive when an emergency comes up where I’ve needed to run DBCC FREEPROCCACHE. Kalen said one should enable “optimize for ad hoc workloads” if you have an adhoc loc.  This stores only a 300-byte stub of the first plan, and if it gets run again, it’ll store the whole thing.  This helps with plan cache bloat.  I have a lot of systems that use prepared statements, and Kalen says we simulate those calls by using sp_executesql.  Cool! Paul did a series of posts last year to debunk various myths and misconceptions around SQL Server.  He continues to debunk things via “DBA Mythbusters”.  You can get a PDF of a bunch of these here.  One of the myths he went over is the number of tempdb data files that you should have.  Back in 2000, the recommendation was to have as many tempdb data files as there are CPU cores on your server.  This no longer holds true due to the numerous cores we have on our servers.  Paul says you should start out with 1/4 to 1/2 the number of cores and work your way up from there.  BUT!  Paul likes what Bob Ward (twitter) says on this topic: 8 or less cores –> set number of files equal to the number of cores Greater than 8 cores –> start with 8 files and increase in blocks of 4 One common myth out there is to set your MAXDOP to 1 for an OLTP workload with high CXPACKET waits.  Instead of that, dig deeper first.  Look for missing indexes, out-of-date statistics, increase the “cost threshold for parallelism” setting, and perhaps set MAXDOP at the query level.  Paul stressed that you should not plan a backup strategy but instead plan a restore strategy.  What are your recoverability requirements?  Once you know that, now plan out your backups. As Paul always does, he talked about DBCC CHECKDB.  He said how fabulous it is.  I didn’t want to interrupt the presentation, so after his session had ended, I asked Paul about the need to run DBCC CHECKDB on your mirror systems.  You could have data corruption occur at the mirror and not at the principal server.  If you aren’t checking for data corruption on your mirror systems, you could be failing over to a corrupt database in the case of a disaster or even a planned failover.  You can’t run DBCC CHECKDB against the mirrored database, but you can run it against a snapshot off the mirrored database.

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  • Best practices for caching search queries

    - by David Esteves
    I am trying to improve performance of my ASP.net Web Api by adding a data cache but I am not sure how exactly to go about it as it seems to be more complex than most caching scenarios. An example is I have a table of Locations and an api to retrieve locations via search, for an autocomplete. /api/location/Londo and the query would be something like SELECT * FROM Locations WHERE Name like 'Londo%' These locations change very infrequently so I would like to cache them to prevent trips to the database for no real reason and improve the response time. Looking at caching options I am using the Windows Azure Appfabric system, the problem is it's just a key/value cache. Since I can only retrieve items based on keys I couldn't actually use it for this scenario as far as Im aware. Is what I am trying to do bad use of a caching system? Should I try looking into NoSql DB which could possibly run as a cache for something like this to improve performance? Should I just cache the entire table/collection in a single key with a specific data structure which could assist with the searching and then do the search upon retrieval of the data?

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  • AWR Performance Report and Read by Other Session Waits

    - by user702295
    For the questions regarding "read by other session" and its relation to "db file sequential/scattered read", the logic is like this: When a "db file sequential/scattered read" is done, the blocks are either already in the cache or on the disk.  Since any operation on blocks is done in the cache and since and the issue is "read by other session" I will relate to the case the blocks are on the disk. Process A is reading the needed block from the disk to the cache.  During that time, if process B (and C and others) need the same block, it will wait on "read by other session".  A and B can be threads of the same process running in parallel or unrelated processes.  For example two processes doing full table scan on mdp_matrix etc. Solutions for that can be lowering the number of processes competing on the same blocks, increasing PCTFREE.  If it is a full table scan, maybe an index is missing that can result in less blocks being read from the cache and so on.

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  • Too much I/O in the morning ?

    - by steveh99999
    Interesting little improvement on a SQL 2005 system I encountered recently….. Some background - this system had a fairly ‘traditional OLTP’ workload ie  heavily used during day – till around 9pm, then had a batch window for several hours, then not much activity in the early hours of the day, until normal workload resumed the following morning. Using perfmon, I noticed that every morning, we would see a big spike in SQL Server I/O when the application started to be used... As it was 2005 I decided to look at what tables were in cache before and after the overnight batch processing ran… ( using DMV equivalent of dbcc memusage that I posted earlier). Here’s what I saw :-     So, contents of data cache split fairly evenly between my 'important/heavily used' tables.   After this:- some application batch processing,backups, DBCC checks and reindexes were run.  A fairly standard batch I'd suggest. Cache contents then looked like this :- Hmmmm – most of cache is now being used by a table I’ve described as ‘unimportant’. Why ? Well, that table was the last to be reindexed…. purely due to luck, as  the reindexing stored procedure performing a loop in alphabetical order through all application tables...  When the application starts to be used again – all this ‘unimportant’ data has to be replaced in cache by data that is heavily used… So, we changed the overnight reindex scripts –  the most heavily accessed tables are now the last to be reindexed. Obvious really, but we did see a significant reduction in early-morning I/O after changing the order of our reindexing.  

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  • Where is a good place to start to learn about custom caching in .Net

    - by John
    I'm looking to make some performance enhancements to our site, but I'm not sure exactly where to begin. We have some custom object caching, but I think that we can do better. Our Business We aggregate news stories on a news type of web site. We get approximately 500-1000 new stories per week. We have index pages that show various lists of the items and details pages that show the individual stories. Our Current Use case: Getting an Individual Story User makes a request The Data Access Layer(DAL) checks to see if the item is in cache and if item is fresh (15 minutes). If the item is not in cache or is not fresh, retrieve the item from SQL Server, save to cache and return to user. Problems with this approach The pull nature of caching means that users have to pay the waiting cost every time that the cache is refreshed. Once a story is published, it changes infrequently and I think that we should replace the pull model with something better. My initial thoughts My initial thought is that stories should ALL be stored locally in some type of dictionary. (Cache or is there another, better way?). If the story is not found, then make a trip to the database, update the local dictionary and send the item back. Since there may be occasional updates to stories, this should be an entirely process from the user. I watched a video by Brent Ozar, How StackOverflow Scales SQL Server, in which Brent states "the fastest database query is the one that you don't make". Where do I start? At this point, I don't know exactly what the solution is. Is it caching? Is there a better way of using local storage? Do I use a Dictionary, OrderedDictionary, List ? It seems daunting and I'm just looking for some good starting points to learn more about how to do this type of optimization.

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  • Graphite Running using daemon tools getting defunct

    - by pradeepchhetri
    I am running carbon-cache.py and carbon-aggregator.py using daemon tools. When I made some changes in the storage-schema.conf and tried to restart the carbon-cache.py, I found that it is becoming zombie very frequently. root 3367 3366 0 03:23 pts/1 00:00:00 supervise carbon-aggregator root 3371 3366 0 03:23 pts/1 00:00:00 supervise carbon-cache root 3373 3367 3 03:23 pts/1 00:00:02 /usr/bin/python /usr/bin/carbon-aggregator.py --debug start root 3379 3372 0 03:23 pts/1 00:00:00 multilog t /var/log/multilog/carbon-cache root 3382 3368 0 03:23 pts/1 00:00:00 multilog t /var/log/multilog/carbon-aggregator root 3638 3371 21 03:24 pts/1 00:00:00 [carbon-cache.py] <defunct> Can someone tell me what may be the reason ?

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  • Squid: caching *.swf with variables

    - by stfn
    I'd recently upgraded my Ubuntu 11.10 x64 server to 12.04. In this process Squid was updated from 2.7 to 3.1. Squid 3.1 has many different options witch broke my setup. So I completely removed squid 2.7 and 3.1 and started from scratch. Everything is now working as before except for 1 thing: caching of .swf files with ?/variables. Squid 3 sees a ? as dynamic content and does not cache it. For example, Squid 2.7 was caching the .swf file at http://ninjakiwi.com/Games/Tower-Defense/Play/Bloons-Tower-Defense-5.html and 3.1 is not. <object id="mov" name="movn" classid="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000" width="800" height="620"> <param name="movie" value="http://www.ninjakiwifiles.com/Games/gameswfs/btd5.swf?v=160512-2"> <param name="allowscriptaccess" value="always"> <param name="bgcolor" value="#000000"> <param name="flashvars" value="file=http://www.ninjakiwifiles.com/Games/gameswfs/btd5-dat.swf?v=280512"> <p>Get Flash play Ninja Kiwi games.</p> </object> It is because of the "?v=160512-2" and "?v=280512" part. This line should be responsible for that: refresh_pattern -i (/cgi-bin/|\?) 0 0% 0 But disabling it still doesn't cache the .swf files. How do I configure Squid 3.1 to cache those files? My current config is: acl manager proto cache_object acl localhost src 127.0.0.1/32 ::1 acl to_localhost dst 127.0.0.0/8 0.0.0.0/32 ::1 acl SSL_ports port 443 acl Safe_ports port 80 # http acl Safe_ports port 21 # ftp acl Safe_ports port 443 # https acl Safe_ports port 70 # gopher acl Safe_ports port 210 # wais acl Safe_ports port 1025-65535 # unregistered ports acl Safe_ports port 280 # http-mgmt acl Safe_ports port 488 # gss-http acl Safe_ports port 591 # filemaker acl Safe_ports port 777 # multiling http acl CONNECT method CONNECT acl localnet src 192.168.2.0-192.168.2.255 acl localnet src 192.168.3.0-192.168.3.255 http_access allow manager localhost http_access deny manager http_access deny !Safe_ports http_access deny CONNECT !SSL_ports http_access allow localhost http_access allow localnet http_access deny all http_port 3128 cache_dir ufs /var/spool/squid 10240 16 256 maximum_object_size 100 MB coredump_dir /var/spool/squid3 refresh_pattern ^ftp: 1440 20% 10080 refresh_pattern ^gopher: 1440 0% 1440 refresh_pattern -i \.(gif|png|jpg|jpeg|ico)$ 10080 90% 43200 override-expire ignore-no-cache ignore-no-store ignore-private refresh_pattern -i \.(iso|avi|wav|mp3|mp4|mpeg|swf|flv|x-flv)$ 43200 90% 432000 override-expire ignore-no-cache ignore-no-store ignore-private refresh_pattern -i \.(deb|rpm|exe|zip|tar|tgz|ram|rar|bin|ppt|doc|tiff)$ 10080 90% 43200 override-expire ignore-no-cache ignore-no-store ignore-private refresh_pattern -i \.index.(html|htm)$ 0 40% 10080 refresh_pattern -i \.(html|htm|css|js)$ 1440 40% 40320 refresh_pattern Packages\.bz2$ 0 20% 4320 refresh-ims refresh_pattern Sources\.bz2$ 0 20% 4320 refresh-ims refresh_pattern Release\.gpg$ 0 20% 4320 refresh-ims refresh_pattern Release$ 0 20% 4320 refresh-ims refresh_pattern . 0 40% 40320 cache_effective_user proxy cache_effective_group proxy

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  • Pre-Loading von Tabellen in 11g

    - by Ulrike Schwinn (DBA Community)
    Tabellen und Indizes in den Cache zu laden, damit möglichst wenig I/O durchgeführt wird, ist eine häufig anzutreffende Anforderung. Diese Technik nennt man auch Pre-Loading oder Pre-Caching von Datenbank Objekten. Die Durchführung ist dabei sehr einfach. Gleich zu Beginn werden spezielle SQL Statements wie SELECT Statements mit Full Table Scan oder Index Scan durchgeführt, damit die entsprechenden Objekte vollständig in den Cache geladen werden können. Besonders interessant ist dieser Aspekt auch im Zusammenhang mit der Erstellung von Testumgebungen. Falls beispielsweise kein Warmup möglich ist, kann man bevor der eigentliche Test durchgeführt wird, bestimmte Tabellen und Indizes mit dieser Technik vorab in den Buffer Cache laden.  Der folgende Artikel zeigt wie man eine Tabelle in 11g in den Buffer Cache laden kann und gibt Tipps zur Durchführung.

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  • last-modified/etags - to include or not?

    - by Kae Verens
    Google's PageSpeed plugin suggests that a website should include Last-Modified and ETag headers: Specify a cache validator "Resources that do not specify a cache validator cannot be refreshed efficiently. Specify a Last-Modified or ETag header to enable cache validation" However, Apache suggests that by not including them at all, we speed up websites by eliminating If-Modified-Since and If-None-Match requests: http://www.askapache.com/htaccess/apache-speed-last-modified.html these are in direct opposition - which should be implemented? I'm leaning towards Apache's suggestion, as when I want a file cached, I don't want it refreshed.

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