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  • How to deal with missing items the SEO way?

    - by Brandon Montgomery
    I am working on a public-facing web site which serves up articles for people to read. After some time, articles become stale and we remove them from the site. My question is this: what is the best way to handle the situation when a search engine visits a URL corresponding to a removed article? Should the app respond with a permanent redirect (301 Moved Permanently) to a "article not found" page, or is there a better way to handle this?

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  • Extend Google AppEngine User in JRuby?

    - by Ryan Montgomery
    I'm working with JRuby and DataMapper running on Google AppEngine. I want to add a property to the AppEngine::User like :active_calendar which is a reference to a Calendar kind. I was able to do something in Python this way using a back reference. Are these possible in JRuby? Is this possible? Do I need to subclass the User? Can I even do that? If so - how? Thanks!

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  • How to tell if SPARC T4 crypto is being used?

    - by danx
    A question that often comes up when running applications on SPARC T4 systems is "How can I tell if hardware crypto accleration is being used?" To review, the SPARC T4 processor includes a crypto unit that supports several crypto instructions. For hardware crypto these include 11 AES instructions, 4 xmul* instructions (for AES GCM carryless multiply), mont for Montgomery multiply (optimizes RSA and DSA), and 5 des_* instructions (for DES3). For hardware hash algorithm optimization, the T4 has the md5, sha1, sha256, and sha512 instructions (the last two are used for SHA-224 an SHA-384). First off, it's easy to tell if the processor T4 crypto instructions—use the isainfo -v command and look for "sparcv9" and "aes" (and other hash and crypto algorithms) in the output: $ isainfo -v 64-bit sparcv9 applications crc32c cbcond pause mont mpmul sha512 sha256 sha1 md5 camellia kasumi des aes ima hpc vis3 fmaf asi_blk_init vis2 vis popc These instructions are not-privileged, so are available for direct use in user-level applications and libraries (such as OpenSSL). Here is the "openssl speed -evp" command shown with the built-in t4 engine and with the pkcs11 engine. Both run the T4 AES instructions, but the t4 engine is faster than the pkcs11 engine because it has less overhead (especially for smaller packet sizes): t-4 $ /usr/bin/openssl version OpenSSL 1.0.0j 10 May 2012 t-4 $ /usr/bin/openssl engine (t4) SPARC T4 engine support (dynamic) Dynamic engine loading support (pkcs11) PKCS #11 engine support t-4 $ /usr/bin/openssl speed -evp aes-128-cbc # t4 engine used by default . . . The 'numbers' are in 1000s of bytes per second processed. type 16 bytes 64 bytes 256 bytes 1024 bytes 8192 bytes aes-128-cbc 487777.10k 816822.21k 986012.59k 1017029.97k 1053543.08k t-4 $ /usr/bin/openssl speed -engine pkcs11 -evp aes-128-cbc engine "pkcs11" set. . . . The 'numbers' are in 1000s of bytes per second processed. type 16 bytes 64 bytes 256 bytes 1024 bytes 8192 bytes aes-128-cbc 31703.58k 116636.39k 350672.81k 696170.50k 993599.49k Note: The "-evp" flag indicates use the OpenSSL "EnVeloPe" API, which gives more accurate results. That's because it tells OpenSSL to use the same API that external programs use when calling OpenSSL libcrypto functions, evp(3openssl). DTrace Shows if T4 Crypto Functions Are Used OK, good enough, the isainfo(1) command shows the instructions are present, but how does one know if they are being used? Chi-Chang Lin, who works on Oracle Solaris performance, wrote a Dtrace script to show if T4 instructions are being executed. To show the T4 instructions are being used, run the following Dtrace script. Look for functions named "t4" and "yf" in the output. The OpenSSL T4 engine uses functions named "t4" and the PKCS#11 engine uses functions named "yf". To demonstrate, I'll first run "openssl speed" with the built-in t4 engine then with the pkcs11 engine. The performance numbers are not valid due to dtrace probes slowing things down. t-4 # dtrace -Z -n ' pid$target::*yf*:entry,pid$target::*t4_*:entry{ @[probemod, probefunc] = count();}' \ -c "/usr/bin/openssl speed -evp aes-128-cbc" dtrace: description 'pid$target::*yf*:entry' matched 101 probes . . . dtrace: pid 2029 has exited libcrypto.so.1.0.0 ENGINE_load_t4 1 libcrypto.so.1.0.0 t4_DH 1 libcrypto.so.1.0.0 t4_DSA 1 libcrypto.so.1.0.0 t4_RSA 1 libcrypto.so.1.0.0 t4_destroy 1 libcrypto.so.1.0.0 t4_free_aes_ctr_NIDs 1 libcrypto.so.1.0.0 t4_init 1 libcrypto.so.1.0.0 t4_add_NID 3 libcrypto.so.1.0.0 t4_aes_expand128 5 libcrypto.so.1.0.0 t4_cipher_init_aes 5 libcrypto.so.1.0.0 t4_get_all_ciphers 6 libcrypto.so.1.0.0 t4_get_all_digests 59 libcrypto.so.1.0.0 t4_digest_final_sha1 65 libcrypto.so.1.0.0 t4_digest_init_sha1 65 libcrypto.so.1.0.0 t4_sha1_multiblock 126 libcrypto.so.1.0.0 t4_digest_update_sha1 261 libcrypto.so.1.0.0 t4_aes128_cbc_encrypt 1432979 libcrypto.so.1.0.0 t4_aes128_load_keys_for_encrypt 1432979 libcrypto.so.1.0.0 t4_cipher_do_aes_128_cbc 1432979 t-4 # dtrace -Z -n 'pid$target::*yf*:entry{ @[probemod, probefunc] = count();}   pid$target::*yf*:entry,pid$target::*t4_*:entry{ @[probemod, probefunc] = count();}' \ -c "/usr/bin/openssl speed -engine pkcs11 -evp aes-128-cbc" dtrace: description 'pid$target::*yf*:entry' matched 101 probes engine "pkcs11" set. . . . dtrace: pid 2033 has exited libcrypto.so.1.0.0 ENGINE_load_t4 1 libcrypto.so.1.0.0 t4_DH 1 libcrypto.so.1.0.0 t4_DSA 1 libcrypto.so.1.0.0 t4_RSA 1 libcrypto.so.1.0.0 t4_destroy 1 libcrypto.so.1.0.0 t4_free_aes_ctr_NIDs 1 libcrypto.so.1.0.0 t4_get_all_ciphers 1 libcrypto.so.1.0.0 t4_get_all_digests 1 libsoftcrypto.so.1 rijndael_key_setup_enc_yf 1 libsoftcrypto.so.1 yf_aes_expand128 1 libcrypto.so.1.0.0 t4_add_NID 3 libsoftcrypto.so.1 yf_aes128_cbc_encrypt 1542330 libsoftcrypto.so.1 yf_aes128_load_keys_for_encrypt 1542330 So, as shown above the OpenSSL built-in t4 engine executes t4_* functions (which are hand-coded assembly executing the T4 AES instructions) and the OpenSSL pkcs11 engine executes *yf* functions. Programmatic Use of OpenSSL T4 engine The OpenSSL t4 engine is used automatically with the /usr/bin/openssl command line. Chi-Chang Lin also points out that if you're calling the OpenSSL API (libcrypto.so) from a program, you must call ENGINE_load_built_engines(), otherwise the built-in t4 engine will not be loaded. You do not call ENGINE_set_default(). That's because "openssl speed -evp" test calls ENGINE_load_built_engines() even though the "-engine" option wasn't specified. OpenSSL T4 engine Availability The OpenSSL t4 engine is available with Solaris 11 and 11.1. For Solaris 10 08/11 (U10), you need to use the OpenSSL pkcs311 engine. The OpenSSL t4 engine is distributed only with the version of OpenSSL distributed with Solaris (and not third-party or self-compiled versions of OpenSSL). The OpenSSL engine implements the AES cipher for Solaris 11, released 11/2011. For Solaris 11.1, released 11/2012, the OpenSSL engine adds optimization for the MD5, SHA-1, and SHA-2 hash algorithms, and DES-3. Although the T4 processor has Camillia and Kasumi block cipher instructions, these are not implemented in the OpenSSL T4 engine. The following charts may help view availability of optimizations. The first chart shows what's available with Solaris CLIs and APIs, the second chart shows what's available in Solaris OpenSSL. Native Solaris Optimization for SPARC T4 This table is shows Solaris native CLI and API support. As such, they are all available with the OpenSSL pkcs11 engine. CLIs: "openssl -engine pkcs11", encrypt(1), decrypt(1), mac(1), digest(1), MD5sum(1), SHA1sum(1), SHA224sum(1), SHA256sum(1), SHA384sum(1), SHA512sum(1) APIs: PKCS#11 library libpkcs11(3LIB) (incluDES Openssl pkcs11 engine), libMD(3LIB), and Solaris kernel modules AlgorithmSolaris 1008/11 (U10)Solaris 11Solaris 11.1 AES-ECB, AES-CBC, AES-CTR, AES-CBC AES-CFB128 XXX DES3-ECB, DES3-CBC, DES2-ECB, DES2-CBC, DES-ECB, DES-CBC XXX bignum Montgomery multiply (RSA, DSA) XXX MD5, SHA-1, SHA-256, SHA-384, SHA-512 XXX SHA-224 X ARCFOUR (RC4) X Solaris OpenSSL T4 Engine Optimization This table is for the Solaris OpenSSL built-in t4 engine. Algorithms listed above are also available through the OpenSSL pkcs11 engine. CLI: openssl(1openssl) APIs: openssl(5), engine(3openssl), evp(3openssl), libcrypto crypto(3openssl) AlgorithmSolaris 11Solaris 11SRU2Solaris 11.1 AES-ECB, AES-CBC, AES-CTR, AES-CBC AES-CFB128 XXX DES3-ECB, DES3-CBC, DES-ECB, DES-CBC X bignum Montgomery multiply (RSA, DSA) X MD5, SHA-1, SHA-256, SHA-384, SHA-512 XX SHA-224 X Source Code Availability Solaris Most of the T4 assembly code that called the new T4 crypto instructions was written by Ferenc Rákóczi of the Solaris Security group, with assistance from others. You can download the Solaris source for this and other parts of Solaris as a few zip files at the Oracle Download website. The relevant source files are generally under directories usr/src/common/crypto/{aes,arcfour,des,md5,modes,sha1,sha2}}/sun4v/. and usr/src/common/bignum/sun4v/. Solaris 11 binary is available from the Oracle Solaris 11 download website. OpenSSL t4 engine The source for the OpenSSL t4 engine, which is based on the Solaris source above, is viewable through the OpenGrok source code browser in directory src/components/openssl/openssl-1.0.0/engines/t4 . You can download the source from the same website or through Mercurial source code management, hg(1). Conclusion Oracle Solaris with SPARC T4 provides a rich set of accelerated cryptographic and hash algorithms. Using the latest update, Solaris 11.1, provides the best set of optimized algorithms, but alternatives are often available, sometimes slightly slower, for releases back to Solaris 10 08/11 (U10). Reference See also these earlier blogs. SPARC T4 OpenSSL Engine by myself, Dan Anderson (2011), discusses the Openssl T4 engine and reviews the SPARC T4 processor for the Solaris 11 release. Exciting Crypto Advances with the T4 processor and Oracle Solaris 11 by Valerie Fenwick (2011) discusses crypto algorithms that were optimized for the T4 processor with the Solaris 11 FCS (11/11) and Solaris 10 08/11 (U10) release. T4 Crypto Cheat Sheet by Stefan Hinker (2012) discusses how to make T4 crypto optimization available to various consumers (such as SSH, Java, OpenSSL, Apache, etc.) High Performance Security For Oracle Database and Fusion Middleware Applications using SPARC T4 (PDF, 2012) discusses SPARC T4 and its usage to optimize application security. Configuring Oracle iPlanet WebServer / Oracle Traffic Director to use crypto accelerators on T4-1 servers by Meena Vyas (2012)

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  • The pros and cons of learning

    - by AaronBertrand
    This week I am at a training course put on by Paul Randal ( blog | twitter ) and Kimberly Tripp ( blog | twitter ) entitled " SQL Immersion ." It is essentially a 5-day deep dive into some of the more important bowels of the Microsoft SQL Server 2008 Internals book they co-wrote with Kalen Delaney, Adam Machanic and Conor Cunningham - with a lot of extra information, insight, experience and interactivity thrown in. I am seeing a lot of benefits from this already. The additional insight around what's...(read more)

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  • Simon Sabin has a great discount for the SQL Server Masterclass

    - by Testas
    Check out Simons blog post to get a discount of £100 for this event http://sqlblogcasts.com/blogs/simons/archive/2010/05/14/paul-and-kimberly-are-coming-the-uk.aspx   Remember as well  Pencil the 17th June in your diary, send an email [email protected] with the title of Masterclass in the subject line. On Friday 25th May we will draw out a name and the winner will have free entrance to a must see seminar on SQL Server from two of the industry’s leading experts. Thanks Chris

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  • Does the tempdb Log file get Zero Initialized at Startup?

    - by Jonathan Kehayias
    While working on a problem today I happened to think about what the impact to startup might be for a really large tempdb transaction log file.  Its fairly common knowledge that data files in SQL Server 2005+ on Windows Server 2003+ can be instant initialized, but the transaction log files can not.  If this is news to you see the following blog posts: Kimberly L. Tripp | Instant Initialization - What, Why and How? In Recovery... | Misconceptions around instant file initialization In Recovery…...(read more)

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  • London User Group Meetings this week (19th/20th May); 26th May-Agile Data Warehousing; 17th June-Kim

    - by tonyrogerson
    Got two user group meetings in London for you, we've also started the Cuppa Corner sessions - the first 3 are up on the site - A trip to First Normal Form, Lookup and Cache Transform in SSIS and Pipeline Limiter in SSIS - we are aiming for at least one per week. WhereScape are doing a breakfast meeting on Agile techniques to Data Warehousing and Kimberly Tripp and Paul Randal are over in June for a 1 day master class. Finally a 3 day performance and monitoring workshop on 22- 24th June in London...(read more)

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  • SQL Server overload in London in June

    - by simonsabin
    After the awesome SQLSocial last night in London we are just about to announce another event next week but in the mean time Paul and Kimberly are doing an Immersion event by Heathrow and have said anyone can come along on the Tuesday or Wednesday nights. If you want to pop along register quick before the space fills up. The event is being held at the Renaissance London Heathrow Hotel .  21 June 2011: Tuesday evening SQL Sentry will present: Tips for Query Tuning with SQL Sentry Plan Explorer...(read more)

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  • ***Master Class competition extended***

    - by Testas
     We have acquired two additional tickets to attend the SQL Server Master Class with Paul Randal and Kimberly Tripp  For a chance to win these coveted tickets In the subject line type MasterClass and email [email protected] before 9pm on Sunday night  The winners will be announced Monday Morning  Don’t worry if you have already purchased a ticket, should you be win, your ticket cost will be reimbursed  

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  • The pros and cons of learning

    - by AaronBertrand
    This week I am at a training course put on by Paul Randal ( blog | twitter ) and Kimberly Tripp ( blog | twitter ) entitled " SQL Immersion ." It is essentially a 5-day deep dive into some of the more important bowels of the Microsoft SQL Server 2008 Internals book they co-wrote with Kalen Delaney, Adam Machanic and Conor Cunningham - with a lot of extra information, insight, experience and interactivity thrown in. I am seeing a lot of benefits from this already. The additional insight around what's...(read more)

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  • SQLTraining in UK in Q3/Q4 of 2011

    - by NeilHambly
    As I prepare to embark on my Immersion training week with Paul & Kimberly from SQLSkills , which is another one of the courses being offered in the UK this year, it seems that these invariably get full very quickly, so don't hang around or you will miss your opportunity to attend them I do know of some other great SQL courses that give you in-depth training and these are the ones that I know of (shown is date order) Sept 12th - 14th (Klaus Aschenbrenner) "Advanced SQL Server Performance...(read more)

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  • YouTube Developers Live: Magnify.net

    YouTube Developers Live: Magnify.net Questions? Please use Google Moderator rather than commenting on this video: goo.gl Join us in a discussion with Steve Rosenbaum (author of _Curation Nation_) and Kimberly Peterson from Magnify.net. We'll discuss content curation and how developers can use the YouTube API to power their own creation applications. From: GoogleDevelopers Views: 0 3 ratings Time: 00:00 More in Science & Technology

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  • Avoid SQL Injection with Parameters

    - by simonsabin
    The best way to avoid SQL Injection is with parameters. With parameters you can’t get SQL Injection. You only get SQL Injection where you are building a SQL statement by concatenating your parameter values in with your SQL statement. Annoyingly many TSQL statements don’t take parameters, CREATE DATABASE for instance, or really annoyingly ALTER USER. In these situations you have to rely on using QUOTENAME or REPLACE to avoid SQL Injection. (Kimberly Tripp takes about this in her recent blog post Little...(read more)

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  • Can I Specify Strings for MySql Table Values?

    - by afterimagedesign
    I have a MySql table that stores the users state and city from a list of states and cities. I specifically coded each state as their two letter shortened version (like WA for Washington and CA for California) and every city has the two letter abbreviation and the city name formated like this: Boulder Colorado would be CO-boulder and Salt Lake City, Utah would be UT-salt-lake-city as to avoid different states with same city name. The PHP inserts the value (UT-salt-lake-city) under the column City, but when I call the variable through PHP, it displays like this: Your location is: UT-salt-lake-city, Utah. To solve this, I've been making this list of variables if ($city == "AL-auburn") { $city = "Auburn"; } else if ($city == "AL-birmingham") { $city = "Birmingham"; } else if ($city == "GA-columbus") { $city = "Columbus"; $state = "Georgia"; } else if ($city == "AL-dothan") { $city = "Dothan"; } else if ($city == "AL-florence") { $city = "Forence"; } else if ($city == "AL-muscle-shoals") { $city = "Muscle Shoals"; } else if ($city == "AL-gadsden-anniston") { $city = "Gadsden Anniston"; } else if ($city == "AL-huntsville") { $city = "Huntsville"; } else if ($city == "AL-decatur") { $city = "Decatur"; } else if ($city == "AL-mobile") { $city = "Mobile"; } else if ($city == "AL-montgomery") { $city = "Montgomery"; } else if ($city == "AL-tuscaloosa") { $city = "Tuscaloosa"; } Is there a way I can shorten this process or at least call it from a separate file so I don't have to copy/paste every time I want to call the location?

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  • Oracle OpenWorld: Oracle WebCenter Customer Appreciation Reception

    - by kellsey.ruppel
    Oracle WebCenter Customer Appreciation Reception Oracle WebCenter partners Fishbowl Solutions, Fujitsu, Keste, Mythics, Redstone Content Solutions, Team Informatics & TekStream invite you to a private cocktail reception at one of San Francisco's finest hotels. Please join us and other Oracle WebCenter customers for heavy hors d'oeuvres and cocktails at this exclusive reception. Tuesday, October 2, 2012 6:30 p.m. – 9:30 p.m. The Palace Hotel Ralston Ballroom 2 New Montgomery Street San Francisco, CA 94105 Don't miss the opportunity to meet and talk with executives from Oracle WebCenter Product Management, Product Marketing and Oracle's premier WebCenter partners. We look forward to seeing you at this event! RSVP Now Please RSVP to http://www.surveymonkey.com/s/OOW12 by September 26, 2012. You will receive an email notification from [email protected] confirming your attendance for this event. Sponsored by:

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  • Cut Caseload Costs, Speed Service Delivery For Social Services

    - by michael.seback
    Lower Caseload Costs, Speedier Service Delivery with New Oracle Social Services Solution Oracle has just introduced a new solution for social services agencies that's designed to help case workers address the challenges of rising workloads and growing demands by citizens for additional services. In the past, IT departments developed custom software in an effort to meet program outcomes. "Because this capability is out of the box with the Oracle solution, there's less complexity for organizations and an overall lower total cost of ownership," says Kimberly Ellison-Taylor, Oracle's executive director of health and human services. "Self service brings costs down to just pennies per interaction and makes it possible for clients to receive government services more quickly," Ellison-Taylor says. read more

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  • Cuda driver, CPU/GPU performances issue

    - by elect
    I implemented a RNS Montgomery exponentiation in Cuda and on cpu for comparison. Everything nice everything fine. It runs on just one SM. However I am going to tell you some strange regression in both cpu/gpu performances. During the devoloping, about two month ago, I was using Cuda 5 preview on Ubuntu 11.04 64b. In this time, I reach the following performances: cpu 460ms gpu 120ms Then one day when I turn on the pc, the graphical environment didnt start. I dont know which was the problem, however I switched to the console and installed again the Cuda driver. At the following boot performances changed: cpu 310ms gpu 80ms I was like Q.Q...uhm ok, nice to see this, but I was wondering how that could be possible However, I went then in holiday for 10 days and I continued developing and optimizing on my notebook (but not the same part of the code, some additional stuff) When I was back, I just updated the source files, and performances came back to 460/120ms.. I couldnt believe it, I tried to install Cuda 5 RC, updating the video driver too... nothing changed... I checked Debug/Release, Cuda computability, but the problem seems being somewhere else.. Looking around the net I found this, I am pretty sure it must have something to do with the driver, because the performance change affected both cpu and gpu Do you have some tips/ideas/suggestions?

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  • Fragmented Log files could be slowing down your database

    - by Fatherjack
    Something that is sometimes forgotten by a lot of DBAs is the fact that database log files get fragmented in the same way that you get fragmentation in a data file. The cause is very different but the effect is the same – too much effort reading and writing data. Data files get fragmented as data is changed through normal system activity, INSERTs, UPDATEs and DELETEs cause fragmentation and most experienced DBAs are monitoring their indexes for fragmentation and dealing with it accordingly. However, you don’t hear about so many working on their log files. How can a log file get fragmented? I’m glad you asked. When you create a database there are at least two files created on the disk storage; an mdf for the data and an ldf for the log file (you can also have ndf files for extra data storage but that’s off topic for now). It is wholly possible to have more than one log file but in most cases there is little point in creating more than one as the log file is written to in a ‘wrap-around’ method (more on that later). When a log file is created at the time that a database is created the file is actually sub divided into a number of virtual log files (VLFs). The number and size of these VLFs depends on the size chosen for the log file. VLFs are also created in the space added to a log file when a log file growth event takes place. Do you have your log files set to auto grow? Then you have potentially been introducing many VLFs into your log file. Let’s get to see how many VLFs we have in a brand new database. USE master GO CREATE DATABASE VLF_Test ON ( NAME = VLF_Test, FILENAME = 'C:\Program Files\Microsoft SQL Server\MSSQL10.ROCK_2008\MSSQL\DATA\VLF_Test.mdf', SIZE = 100, MAXSIZE = 500, FILEGROWTH = 50 ) LOG ON ( NAME = VLF_Test_Log, FILENAME = 'C:\Program Files\Microsoft SQL Server\MSSQL10.ROCK_2008\MSSQL\DATA\VLF_Test_log.ldf', SIZE = 5MB, MAXSIZE = 250MB, FILEGROWTH = 5MB ); go USE VLF_Test go DBCC LOGINFO; The results of this are firstly a new database is created with specified files sizes and the the DBCC LOGINFO results are returned to the script editor. The DBCC LOGINFO results have plenty of interesting information in them but lets first note there are 4 rows of information, this relates to the fact that 4 VLFs have been created in the log file. The values in the FileSize column are the sizes of each VLF in bytes, you will see that the last one to be created is slightly larger than the others. So, a 5MB log file has 4 VLFs of roughly 1.25 MB. Lets alter the CREATE DATABASE script to create a log file that’s a bit bigger and see what happens. Alter the code above so that the log file details are replaced by LOG ON ( NAME = VLF_Test_Log, FILENAME = 'C:\Program Files\Microsoft SQL Server\MSSQL10.ROCK_2008\MSSQL\DATA\VLF_Test_log.ldf', SIZE = 1GB, MAXSIZE = 25GB, FILEGROWTH = 1GB ); With a bigger log file specified we get more VLFs What if we make it bigger again? LOG ON ( NAME = VLF_Test_Log, FILENAME = 'C:\Program Files\Microsoft SQL Server\MSSQL10.ROCK_2008\MSSQL\DATA\VLF_Test_log.ldf', SIZE = 5GB, MAXSIZE = 250GB, FILEGROWTH = 5GB ); This time we see more VLFs are created within our log file. We now have our 5GB log file comprised of 16 files of 320MB each. In fact these sizes fall into all the ranges that control the VLF creation criteria – what a coincidence! The rules that are followed when a log file is created or has it’s size increased are pretty basic. If the file growth is lower than 64MB then 4 VLFs are created If the growth is between 64MB and 1GB then 8 VLFs are created If the growth is greater than 1GB then 16 VLFs are created. Now the potential for chaos comes if the default values and settings for log file growth are used. By default a database log file gets a 1MB log file with unlimited growth in steps of 10%. The database we just created is 6 MB, let’s add some data and see what happens. USE vlf_test go -- we need somewhere to put the data so, a table is in order IF OBJECT_ID('A_Table') IS NOT NULL DROP TABLE A_Table go CREATE TABLE A_Table ( Col_A int IDENTITY, Col_B CHAR(8000) ) GO -- Let's check the state of the log file -- 4 VLFs found EXECUTE ('DBCC LOGINFO'); go -- We can go ahead and insert some data and then check the state of the log file again INSERT A_Table (col_b) SELECT TOP 500 REPLICATE('a',2000) FROM sys.columns AS sc, sys.columns AS sc2 GO -- insert 500 rows and we get 22 VLFs EXECUTE ('DBCC LOGINFO'); go -- Let's insert more rows INSERT A_Table (col_b) SELECT TOP 2000 REPLICATE('a',2000) FROM sys.columns AS sc, sys.columns AS sc2 GO 10 -- insert 2000 rows, in 10 batches and we suddenly have 107 VLFs EXECUTE ('DBCC LOGINFO'); Well, that escalated quickly! Our log file is split, internally, into 107 fragments after a few thousand inserts. The same happens with any logged transactions, I just chose to illustrate this with INSERTs. Having too many VLFs can cause performance degradation at times of database start up, log backup and log restore operations so it’s well worth keeping a check on this property. How do we prevent excessive VLF creation? Creating the database with larger files and also with larger growth steps and actively choosing to grow your databases rather than leaving it to the Auto Grow event can make sure that the growths are made with a size that is optimal. How do we resolve a situation of a database with too many VLFs? This process needs to be done when the database is under little or no stress so that you don’t affect system users. The steps are: BACKUP LOG YourDBName TO YourBackupDestinationOfChoice Shrink the log file to its smallest possible size DBCC SHRINKFILE(FileNameOfTLogHere, TRUNCATEONLY) * Re-size the log file to the size you want it to, taking in to account your expected needs for the coming months or year. ALTER DATABASE YourDBName MODIFY FILE ( NAME = FileNameOfTLogHere, SIZE = TheSizeYouWantItToBeIn_MB) * – If you don’t know the file name of your log file then run sp_helpfile while you are connected to the database that you want to work on and you will get the details you need. The resize step can take quite a while This is already detailed far better than I can explain it by Kimberley Tripp in her blog 8-Steps-to-better-Transaction-Log-throughput.aspx. The result of this will be a log file with a VLF count according to the bullet list above. Knowing when VLFs are being created By complete coincidence while I have been writing this blog (it’s been quite some time from it’s inception to going live) Jonathan Kehayias from SQLSkills.com has written a great article on how to track database file growth using Event Notifications and Service Broker. I strongly recommend taking a look at it as this is going to catch any sneaky auto grows that take place and let you know about them right away. Hassle free monitoring of VLFs If you are lucky or wise enough to be using SQL Monitor or another monitoring tool that let’s you write your own custom metrics then you can keep an eye on this very easily. There is a custom metric for VLFs (written by Stuart Ainsworth) already on the site and there are some others there are very useful so take a moment or two to look around while you are there. Resources MSDN – http://msdn.microsoft.com/en-us/library/ms179355(v=sql.105).aspx Kimberly Tripp from SQLSkills.com – http://www.sqlskills.com/BLOGS/KIMBERLY/post/8-Steps-to-better-Transaction-Log-throughput.aspx Thomas LaRock at Simple-Talk.com – http://www.simple-talk.com/sql/database-administration/monitoring-sql-server-virtual-log-file-fragmentation/ Disclosure I am a Friend of Red Gate. This means that I am more than likely to say good things about Red Gate DBA and Developer tools. No matter how awesome I make them sound, take the time to compare them with other products before you contact the Red Gate sales team to make your order.

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  • why C clock() returns 0

    - by eddy ed
    I've got something like this: clock_t start, end; start=clock(); something_else(); end=clock(); printf("\nClock cycles are: %d - %d\n",start,end); and I always get as an output "Clock cycles are: 0 - 0" Any idea why this happens? (Just to give little detail, the something_else() function performs a left-to-right exponentiation using montgomery represantation, moreover I don't know for certain that the something_else() function does indeed take some not negligible time.) This is on Linux. The result of uname -a is: Linux snowy.*****.ac.uk 2.6.32-71.el6.x86_64 #1 SMP Fri May 20 03:51:51 BST 2011 x86_64 x86_64 x86_64 GNU/Linux

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  • Consolidation Strategy References

    - by BuckWoody
    I have a presentation that I give on SQL Server Consolidation Strategies, and in that presentation I talk about a few links that are useful. Here are some that I’ve found – feel free to comment on more, or if these links go stale:   Consolidation using SQL Server: http://msdn.microsoft.com/en-us/library/ee692366.aspx SQL Server Consolidation Guidance:  http://msdn.microsoft.com/en-us/library/ee819082.aspx   More references for SQL Server and Hyper-V: http://www.sqlskills.com/BLOGS/KIMBERLY/post/Virtualization-with-SQL-Server.aspx Quick overview of Virtual Server licensing implications: http://www.microsoft.com/uk/licensing/morethan250/learn/virtualisation.mspx SQL Server and Hyper-V best practices: http://sqlcat.com/whitepapers/archive/2008/10/03/running-sql-server-2008-in-a-hyper-v-environment-best-practices-and-performance-recommendations.aspx High-Availability and Hyper-V: http://technet.microsoft.com/en-us/magazine/2008.10.higha.aspx Virtualization Calculator: http://www.microsoft.com/Windowsserver2008/en/us/hyperv-calculators.aspx   May not be current, but here’s a whitepaper from VMWare for SQL Server: http://www.vmware.com/files/pdf/SQLServerWorkloads.pdf More information on SQL Server and VMWare: http://blogs.msdn.com/cindygross/archive/2009/10/23/considerations-for-installing-sql-server-on-vmware.aspx   Server Virtualization Validation Program: http://www.windowsservercatalog.com/svvp.aspx?svvppage=svvp.htm Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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  • Most Unprofessional Workplace

    - by TehGrumpyCoder
    I've worked lots of places in lots of roles: Delivery truck driver, Boilermaker, antenna rigger, Professional Musician, Electronic Technician, Electrical Engineer, and for most of my career: Software Turkey. I want to say this large company is the most unprofessional place I've ever worked, but then I think about other jobs such as TTI that stiffed us all for 10 months salary -- or had us work 2-1/2 years at 66% however you want to look at it, or maybe NeoPlanet with a cast from a bad sitcom running the show, I could go on, but I digress (as usual). So maybe this place isn't the *most* unprofessional, but the personnel rank up there. I'm in a small room off a factory. There are 3 managerial offices, and 36 common-folk of various skill-sets in a variety of single to quad cubicles. No matter where you sit though, because of the layout and location, you've got a hard wall as one wall of your cubicle. Because of that hard wall, everything echoes. I get off the phone, and the guy in the next cubicle makes a comment in response to my phone conversation... I hate that it can be heard and I hate that they do that! These people have no problem yelling from cube to cube to carry on running conversations some of which are actually work-related. There's a lady two cubes away that talks so loud I can clearly hear every phone conversation she has... all work-related but still... Then the one in the next cubicle must have been raised on a farm because there's only one volume setting: LOUD... "HEY MARGE, CAN I GET IN FOR A QUICK APPOINTMENT AFTER WORK TONIGHT?" ... sigh Also that cube is the 'party cube' so that's where all the candy, cake, donuts, and leftovers sits. Anything MzLoud brings in has to have a verbal recipe associated with it at least 10 times during the day, and of course at volume. I've had running conversations over the top of my cube from people in the next one on each side. The weird thing is... the boss sits with an open door closer to this whole fiasco than me. So I wear a pair of Bose noise-cancelling headphones, and crank up Kenny Burrell, Herb Ellis, Wes Montgomery, or Jimmy Smith to the point I can't hear the racket... what the heck, I already have a hearing loss from playing guitar.

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  • Missing Indexes DMV Report, 3 billion Impact!

    - by Tara Kizer
    We’ve been having some major performance issues with one of the applications that I support.  The database is on SQL Server 2005 and is about 150GB in size.  We’ve identified a couple of issues already on the database side.  The first issue is that some query (or maybe several queries) is getting a bad execution plan at some point in time during the day.  When it occurs, database performance comes to a grinding halt.  We know it’s a bad execution plan as running DBCC FREEPROCCACHE immediately resolves the problem system-wide.  As we have not yet identified the problematic query, we’ve put a temporary solution in place that frees the procedure cache on an hourly basis via a SQL Agent job.  This is not ideal, but it is getting us through the day without a major problem.  We are actively working on identifying the problematic query and hope to disable the SQL Agent job soon. Earlier this week, we had a major slowdown for one of the processes of this application.  I was unable to find any database performance issues, but I continued to investigate it.  One of things that I typically do when investigating database performance issues is run the “Missing Indexes DMV Report” (that’s what I call it at least).  When analyzing the output of that report, I immediately dismiss anything under 1 million “Impact” as I want to target the “low-hanging fruit” initially.  When I ran the report earlier this week, I was shocked to find a suggested index with an impact of over 3 billion! Do I win a prize for the highest impact?  Has anyone seen a value higher than mine?  My exact value was 3154284120.67765. The performance issue from earlier this week ended up being an application problem, but it also brought to light a much needed index.  I had previously seen this index come up in that report but always with a much lower impact.  I had never considered it as the index’s selectivity is very low.  It’s a composite index with three columns.  The first column is not selective, the first two columns are not selective, and the three columns together are not selective.  In fact, no matter how I order it, the index will not be selective at all.  I briefly discussed this with Kimberly Tripp, and she said that this was okay for covering indexes.  Selectivity is irrelevant for a covering index.  She indicated that she’s even created indexes with gender as the first column in the index.  I’ve got lots to learn still!

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