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  • Designing a social network with CQRS, graph databases and relational databases in mind

    - by Siraj Mansour
    I have done quite an amount of research on the topic so far, but i couldn't come up with a conclusion to make up my mind. I am designing a social network and during my research i stumbled upon graph databases, i found neo4j pretty interesting for user relations and traversing through nodes. I also thought of using a relational database such as MS-SQL or MySQL to store entity data only and depending on neo4j for connections between entities. Of course this means more work in my application to store and pull data in and out of 2 different sources. My first question : Is using this approach (graph + relational) a good approach for designing my social network keeping in mind that users on social networks don't have to in synch with real data by split second ? What are the positives and negatives of this approach ? My Second question : I've been doing some reading on CQRS and as i understood it is mostly useful for collaborative environments, and environments where users see a lot of "stale" data. social networks has shared comments, events, etc .. and many users query or update the same data. Could CQRS be a helpful approach ? Would it give any performance/scalability benefits or non-useful complexity ? Is it fairly applicable with my possible choice of (graph + relational) databases approach mentioned in the question above ? My purpose is to know if the approaches i have mentioned above seem good enough for the business context.

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  • Big Data – Operational Databases Supporting Big Data – Key-Value Pair Databases and Document Databases – Day 13 of 21

    - by Pinal Dave
    In yesterday’s blog post we learned the importance of the Relational Database and NoSQL database in the Big Data Story. In this article we will understand the role of Key-Value Pair Databases and Document Databases Supporting Big Data Story. Now we will see a few of the examples of the operational databases. Relational Databases (Yesterday’s post) NoSQL Databases (Yesterday’s post) Key-Value Pair Databases (This post) Document Databases (This post) Columnar Databases (Tomorrow’s post) Graph Databases (Tomorrow’s post) Spatial Databases (Tomorrow’s post) Key Value Pair Databases Key Value Pair Databases are also known as KVP databases. A key is a field name and attribute, an identifier. The content of that field is its value, the data that is being identified and stored. They have a very simple implementation of NoSQL database concepts. They do not have schema hence they are very flexible as well as scalable. The disadvantages of Key Value Pair (KVP) database are that they do not follow ACID (Atomicity, Consistency, Isolation, Durability) properties. Additionally, it will require data architects to plan for data placement, replication as well as high availability. In KVP databases the data is stored as strings. Here is a simple example of how Key Value Database will look like: Key Value Name Pinal Dave Color Blue Twitter @pinaldave Name Nupur Dave Movie The Hero As the number of users grow in Key Value Pair databases it starts getting difficult to manage the entire database. As there is no specific schema or rules associated with the database, there are chances that database grows exponentially as well. It is very crucial to select the right Key Value Pair Database which offers an additional set of tools to manage the data and provides finer control over various business aspects of the same. Riak Rick is one of the most popular Key Value Database. It is known for its scalability and performance in high volume and velocity database. Additionally, it implements a mechanism for collection key and values which further helps to build manageable system. We will further discuss Riak in future blog posts. Key Value Databases are a good choice for social media, communities, caching layers for connecting other databases. In simpler words, whenever we required flexibility of the data storage keeping scalability in mind – KVP databases are good options to consider. Document Database There are two different kinds of document databases. 1) Full document Content (web pages, word docs etc) and 2) Storing Document Components for storage. The second types of the document database we are talking about over here. They use Javascript Object Notation (JSON) and Binary JSON for the structure of the documents. JSON is very easy to understand language and it is very easy to write for applications. There are two major structures of JSON used for Document Database – 1) Name Value Pairs and 2) Ordered List. MongoDB and CouchDB are two of the most popular Open Source NonRelational Document Database. MongoDB MongoDB databases are called collections. Each collection is build of documents and each document is composed of fields. MongoDB collections can be indexed for optimal performance. MongoDB ecosystem is highly available, supports query services as well as MapReduce. It is often used in high volume content management system. CouchDB CouchDB databases are composed of documents which consists fields and attachments (known as description). It supports ACID properties. The main attraction points of CouchDB are that it will continue to operate even though network connectivity is sketchy. Due to this nature CouchDB prefers local data storage. Document Database is a good choice of the database when users have to generate dynamic reports from elements which are changing very frequently. A good example of document usages is in real time analytics in social networking or content management system. Tomorrow In tomorrow’s blog post we will discuss about various other Operational Databases supporting Big Data. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Big Data, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL

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  • Windows 7 client can't connect to CentOS PPTP VPN

    - by Chris
    Have a Macintosh (10.8.2) that connects just fine to a CentOS 6.0 virtual private server (OpenVZ, with PPP added by the host) via PPTP. A Windows 7 Home Premium client (virtualized in Sun's Virtual Box), on the same computer, using the same Ethernet connection, cannot connect to the Linux VPN server. I have iptables disabled (for testing) on the Linux box. I have the Windows firewall turned off. /var/log/messages looks like this, for a Windows connection: Oct 12 18:44:30 production pptpd[1880]: CTRL: Client 66.104.246.168 control connection started Oct 12 18:44:30 production pptpd[1880]: CTRL: Starting call (launching pppd, opening GRE) Oct 12 18:44:30 production pppd[1881]: Plugin /usr/lib/pptpd/pptpd-logwtmp.so loaded. Oct 12 18:44:30 production pppd[1881]: pptpd-logwtmp: $Version$ Oct 12 18:44:30 production pppd[1881]: pppd options in effect: Oct 12 18:44:30 production pppd[1881]: debug#011#011# (from /etc/ppp/options.pptpd) Oct 12 18:44:30 production pppd[1881]: nologfd#011#011# (from /etc/ppp/options.pptpd) Oct 12 18:44:30 production pppd[1881]: dump#011#011# (from /etc/ppp/options.pptpd) Oct 12 18:44:30 production pppd[1881]: plugin /usr/lib/pptpd/pptpd-logwtmp.so#011#011# (from command line) Oct 12 18:44:30 production pppd[1881]: require-mschap-v2#011#011# (from /etc/ppp/options.pptpd) Oct 12 18:44:30 production pppd[1881]: refuse-pap#011#011# (from /etc/ppp/options.pptpd) Oct 12 18:44:30 production pppd[1881]: refuse-chap#011#011# (from /etc/ppp/options.pptpd) Oct 12 18:44:30 production pppd[1881]: refuse-mschap#011#011# (from /etc/ppp/options.pptpd) Oct 12 18:44:30 production pppd[1881]: name pptpd#011#011# (from /etc/ppp/options.pptpd) Oct 12 18:44:30 production pppd[1881]: pptpd-original-ip 66.104.246.168#011#011# (from command line) Oct 12 18:44:30 production pppd[1881]: 115200#011#011# (from command line) Oct 12 18:44:30 production pppd[1881]: lock#011#011# (from /etc/ppp/options.pptpd) Oct 12 18:44:30 production pppd[1881]: local#011#011# (from command line) Oct 12 18:44:30 production pppd[1881]: novj#011#011# (from /etc/ppp/options.pptpd) Oct 12 18:44:30 production pppd[1881]: novjccomp#011#011# (from /etc/ppp/options.pptpd) Oct 12 18:44:30 production pppd[1881]: ipparam 66.104.246.168#011#011# (from command line) Oct 12 18:44:30 production pppd[1881]: proxyarp#011#011# (from /etc/ppp/options.pptpd) Oct 12 18:44:30 production pppd[1881]: 192.168.97.1:192.168.97.10#011#011# (from command line) Oct 12 18:44:30 production pppd[1881]: nobsdcomp#011#011# (from /etc/ppp/options.pptpd) Oct 12 18:44:30 production pppd[1881]: require-mppe-128#011#011# (from /etc/ppp/options.pptpd) Oct 12 18:44:30 production pppd[1881]: mppe-stateful#011#011# (from /etc/ppp/options.pptpd) Oct 12 18:44:30 production pppd[1881]: pppd 2.4.5 started by root, uid 0 Oct 12 18:44:30 production pppd[1881]: Using interface ppp0 Oct 12 18:44:30 production pppd[1881]: Connect: ppp0 <--> /dev/pts/1 (At this point the Windows machine displays a dialog, reading: "Verifying user name and password...") Oct 12 18:45:00 production pppd[1881]: LCP: timeout sending Config-Requests Oct 12 18:45:00 production pppd[1881]: Connection terminated. Oct 12 18:45:00 production pppd[1881]: Modem hangup Oct 12 18:45:00 production pppd[1881]: Exit. Oct 12 18:45:00 production pptpd[1880]: GRE: read(fd=6,buffer=8059660,len=8196) from PTY failed: status = -1 error = Input/output error, usually caused by unexpected termination of pppd, check option syntax and pppd logs Oct 12 18:45:00 production pptpd[1880]: CTRL: PTY read or GRE write failed (pty,gre)=(6,7) Oct 12 18:45:00 production pptpd[1880]: CTRL: Client 66.104.246.168 control connection finished The Macintosh connecting looks like this in /var/log/messages: Oct 12 18:50:49 production pptpd[1920]: CTRL: Client 66.104.246.168 control connection started Oct 12 18:50:49 production pptpd[1920]: CTRL: Starting call (launching pppd, opening GRE) Oct 12 18:50:49 production pppd[1921]: Plugin /usr/lib/pptpd/pptpd-logwtmp.so loaded. Oct 12 18:50:49 production pppd[1921]: pptpd-logwtmp: $Version$ Oct 12 18:50:49 production pppd[1921]: pppd options in effect: Oct 12 18:50:49 production pppd[1921]: debug#011#011# (from /etc/ppp/options.pptpd) Oct 12 18:50:49 production pppd[1921]: nologfd#011#011# (from /etc/ppp/options.pptpd) Oct 12 18:50:49 production pppd[1921]: dump#011#011# (from /etc/ppp/options.pptpd) Oct 12 18:50:49 production pppd[1921]: plugin /usr/lib/pptpd/pptpd-logwtmp.so#011#011# (from command line) Oct 12 18:50:49 production pppd[1921]: require-mschap-v2#011#011# (from /etc/ppp/options.pptpd) Oct 12 18:50:49 production pppd[1921]: refuse-pap#011#011# (from /etc/ppp/options.pptpd) Oct 12 18:50:49 production pppd[1921]: refuse-chap#011#011# (from /etc/ppp/options.pptpd) Oct 12 18:50:49 production pppd[1921]: refuse-mschap#011#011# (from /etc/ppp/options.pptpd) Oct 12 18:50:49 production pppd[1921]: name pptpd#011#011# (from /etc/ppp/options.pptpd) Oct 12 18:50:49 production pppd[1921]: pptpd-original-ip 66.104.246.168#011#011# (from command line) Oct 12 18:50:49 production pppd[1921]: 115200#011#011# (from command line) Oct 12 18:50:49 production pppd[1921]: lock#011#011# (from /etc/ppp/options.pptpd) Oct 12 18:50:49 production pppd[1921]: local#011#011# (from command line) Oct 12 18:50:49 production pppd[1921]: novj#011#011# (from /etc/ppp/options.pptpd) Oct 12 18:50:49 production pppd[1921]: novjccomp#011#011# (from /etc/ppp/options.pptpd) Oct 12 18:50:49 production pppd[1921]: ipparam 66.104.246.168#011#011# (from command line) Oct 12 18:50:49 production pppd[1921]: proxyarp#011#011# (from /etc/ppp/options.pptpd) Oct 12 18:50:49 production pppd[1921]: 192.168.97.1:192.168.97.10#011#011# (from command line) Oct 12 18:50:49 production pppd[1921]: nobsdcomp#011#011# (from /etc/ppp/options.pptpd) Oct 12 18:50:49 production pppd[1921]: require-mppe-128#011#011# (from /etc/ppp/options.pptpd) Oct 12 18:50:49 production pppd[1921]: mppe-stateful#011#011# (from /etc/ppp/options.pptpd) Oct 12 18:50:49 production pppd[1921]: pppd 2.4.5 started by root, uid 0 Oct 12 18:50:49 production pppd[1921]: Using interface ppp0 Oct 12 18:50:49 production pppd[1921]: Connect: ppp0 <--> /dev/pts/1 Oct 12 18:50:52 production pppd[1921]: MPPE 128-bit stateless compression enabled Oct 12 18:50:52 production pppd[1921]: Unsupported protocol 'IPv6 Control Protocol' (0x8057) received Oct 12 18:50:52 production pppd[1921]: Unsupported protocol 'Apple Client Server Protocol Control' (0x8235) received Oct 12 18:50:52 production pppd[1921]: Cannot determine ethernet address for proxy ARP Oct 12 18:50:52 production pppd[1921]: local IP address 192.168.97.1 Oct 12 18:50:52 production pppd[1921]: remote IP address 192.168.97.10 Oct 12 18:50:52 production pppd[1921]: pptpd-logwtmp.so ip-up ppp0 chris 66.104.246.168 I'm baffled...

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  • SQL Server v.Next (Denali) : More on contained databases and "contained users"

    - by AaronBertrand
    One of the reasons for contained databases (see my previous post ) is to allow for a more seamless transition when moving a database from one server to another. One of the biggest complications in doing so is making sure that all of the logins are in place on the new server. Contained databases help solve this issue by creating a new type of user: a database-level user with a password. I want to stress that this is not the same concept as a user without a login , which serves a completely different...(read more)

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  • Understanding the problem when things break in production

    - by bitcycle
    Scenario: You push to production The push broke multiple things That same build did not break qa or dev As a developer, you don't have prod access. There is lots of pressure from above to get things working agian. Specifics: PHP/MVC application that is API-driven in Zend. Deployed to a few servers. My question: While investigating, lets say I have a hunch that something is wrong. But, I don't know for sure. And, of course, I can't test things in production. If I have a suggested fix based on that hunch, would it be wise to try and apply it and see if it works, before understanding what the problem is?

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  • Term for Production Rollback

    - by trainer
    The firm I work at keeps a copy of the compiled source code on production. So basically on our Production server, we have two folders: ProductionServer\SourceCode\ ProductionServer\SourceCodeRollback\ The Rollback folder always contains one version older code. This is done so that on deployment nights, if something is wrong with the new code, the deployer(who is not familiar with source control software) has the older version to revert back to. My question is: Is there an official computer science term/nomenclature for the Rollback folder? Or is "Rollback" itself the official term?

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  • Unable to send email on production server with ASP.NET MVC

    - by Davide Vosti
    I have a simple ASP.NET MVC application with a contact page. In my development machine (local) I can send successfully emails (I specify host and credentials), but on the production server this doesn't work and I get this error: System.Net.Mail.SmtpFailedRecipientException: Mailbox unavailable. The server response was: Requested action not taken: mailbox unavailable or not local at System.Net.Mail.SmtpTransport.SendMail... The server is in my LAN (the mail server too). I tried with multiple accounts but I have errors every time. Credentials for the account are provided at runtime with smtp.Credentials = new NetworkCredential("username", "password"); Any idea? Thanks

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  • Safely deploying changes to production servers

    - by oazabir
    When you deploy incremental changes on a production server, which is running and live all the time, you some times see error messages like “Compiler Error Message: The Type ‘XXX’ exists in both…”. Sometimes you find Application_Start event not firing although you shipped a new class, dll or web.config. Sometimes you find static variables not getting initialized and so on. There are so many weird things happen on webservers when you incrementally deploy changes to the server and the server has been up and running for several weeks. So, I came up with a full proof house keeping steps that we always do whenever we deploy some incremental change to our websites. These steps ensure that the web sites are properly recycled , cached are cleared, all the data stored at Application level is initialized. First of all you should have multiple web servers behind load balancer. This way you can take one server our of the production traffic, do your deployment and house keeping tasks like restarting IIS, and then put it back. Then you can do it for the second server and so on. This ensures there’s no outage for customer. If you can do it reasonable fast, hopefully customers won’t notice discrepancy between the servers some having new code and some having old code. You should only do this when your changes aren’t drastic. For ex, you aren’t delivering a complete revamped UI. In that case, some users hitting server1 with latest UI will suddenly get a completely different experience and then on next page refresh, they might hit server2 with old code and get a totally different experience. This works for incremental non-dramatic changes only.   During deployment you should follow these steps: Take server X out of load balancer so that it does not get any traffic. Stop all windows services on the server. Stop IIS. Delete the Temporary ASP.NET folders of all .NET versions incase you have multiple .NET versions running. You can follow this link. Deploy the changes. Flush any distributed cache you have, for ex, Velocity or Memcached. Start IIS. Start the windows services on the server. Warm up all websites by hitting major URLs on the websites. You should have some automated script to do this. You can use tinyget to hit some major URLs, especially pages that take a lot of time to compile. Read my post on keeping websites warm with zero coding. Put server X back to load balancer so that it starts receiving traffic. That’s it. It should give you a clean deployment and prevent unexpected errors. You should print these steps and hang on the desk of your deployment guys so that they never forget during deployment pressure.

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  • mysql show databases not showing databases that are in /opt/bitnami/mysql/data directory

    - by hgolov
    and thank you for taking the time to look at my question. I have an ebs-backed ec2 ubuntu server which is running but unreachable. ** There are very stupidly no recent backups ** I made a snapshot of the block, created a volume, spun up a new instance, attached the new volume. I see all the data from my site in the /opt/bitnami/mysql/data directory, but when I go into the mysql console, it shows only information_schema and test when I type show databases; How can I 'point' mysql to the correct folder? Thank you!

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  • Would a model like this translate well to a document or graph database?

    - by Eric
    I'm trying to understand what types of models that I have traditionally persisted relationally would translate well to some kind of NoSQL database. Suppose I have a model with the following relationships: Product 1-----0..N Order Customer 1-----0..N Order And suppose I need to frequently query things like All Orders, All Products, All Customers, All Orders for Given Customer, All Orders for Given Product. My feeling is that this kind of model would not denormalize cleanly - If I had Product and Customer documents with embedded Orders, both documents would have duplicate orders. So I think I'd need separate documents for all three entities. Does a characteristic like this typically indicate that a document database is not well suited for a given model? Generally speaking, would a document database perform as well as a relational database in this kind of situation? I know very little about graph databases, but I understand that a graph database handles relationships more performantly than a document database - would a graph database be suited for this kind of model?

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  • Creating a development environment from a shared hosting production environment (LAMP)

    - by bobo
    The production server is shared, I don't have access to php.ini and httpd.conf and most PHP settings cannot be set or overrided using ini_set PHP function. So I would like to create a local development environment having configurations as close as it can be to those of the production environment (LAMP). I don't have shell access to the server but using exec PHP function to run some simple commands is possible. I am using Windows XP Pro and I am going to install on VMWare a linux distribution that is more or less the same as the production server. However, installing apache, mysql and php, and then configuring them like those on the production server is not a easy task. It would be great if there exists any tools that are useful in this situation, tools that can analyze/ inspect the production server and then produce something that can help replicating the environment would be useful. If not, what should I be aware of when I try to manually replicate the production environment?

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  • Big Data – Operational Databases Supporting Big Data – Columnar, Graph and Spatial Database – Day 14 of 21

    - by Pinal Dave
    In yesterday’s blog post we learned the importance of the Key-Value Pair Databases and Document Databases in the Big Data Story. In this article we will understand the role of Columnar, Graph and Spatial Database supporting Big Data Story. Now we will see a few of the examples of the operational databases. Relational Databases (The day before yesterday’s post) NoSQL Databases (The day before yesterday’s post) Key-Value Pair Databases (Yesterday’s post) Document Databases (Yesterday’s post) Columnar Databases (Tomorrow’s post) Graph Databases (Today’s post) Spatial Databases (Today’s post) Columnar Databases  Relational Database is a row store database or a row oriented database. Columnar databases are column oriented or column store databases. As we discussed earlier in Big Data we have different kinds of data and we need to store different kinds of data in the database. When we have columnar database it is very easy to do so as we can just add a new column to the columnar database. HBase is one of the most popular columnar databases. It uses Hadoop file system and MapReduce for its core data storage. However, remember this is not a good solution for every application. This is particularly good for the database where there is high volume incremental data is gathered and processed. Graph Databases For a highly interconnected data it is suitable to use Graph Database. This database has node relationship structure. Nodes and relationships contain a Key Value Pair where data is stored. The major advantage of this database is that it supports faster navigation among various relationships. For example, Facebook uses a graph database to list and demonstrate various relationships between users. Neo4J is one of the most popular open source graph database. One of the major dis-advantage of the Graph Database is that it is not possible to self-reference (self joins in the RDBMS terms) and there might be real world scenarios where this might be required and graph database does not support it. Spatial Databases  We all use Foursquare, Google+ as well Facebook Check-ins for location aware check-ins. All the location aware applications figure out the position of the phone with the help of Global Positioning System (GPS). Think about it, so many different users at different location in the world and checking-in all together. Additionally, the applications now feature reach and users are demanding more and more information from them, for example like movies, coffee shop or places see. They are all running with the help of Spatial Databases. Spatial data are standardize by the Open Geospatial Consortium known as OGC. Spatial data helps answering many interesting questions like “Distance between two locations, area of interesting places etc.” When we think of it, it is very clear that handing spatial data and returning meaningful result is one big task when there are millions of users moving dynamically from one place to another place & requesting various spatial information. PostGIS/OpenGIS suite is very popular spatial database. It runs as a layer implementation on the RDBMS PostgreSQL. This makes it totally unique as it offers best from both the worlds. Courtesy: mushroom network Tomorrow In tomorrow’s blog post we will discuss about very important components of the Big Data Ecosystem – Hive. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Big Data, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL

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  • Shrink Partition on Production Server

    - by Campo
    SO our production server was only setup with one large partition. I have setup a standby server and properly partitioned it. Now the boss wants the production environment's partition shrunk. It is an HP DL380 G5 We have 4 hot swap drives in a raid 5. How best should I go about doing this. Seems like a bad idea to me. Should I use windows or HP to do the partitioning? What should I be aware of in a production environment? The idea is to put the site (Inetpub) on a separate partition instead of the C: drive. How much downtime should I expect? Is this a terrible idea? Anything else I have missed?

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  • Big Data – Operational Databases Supporting Big Data – RDBMS and NoSQL – Day 12 of 21

    - by Pinal Dave
    In yesterday’s blog post we learned the importance of the Cloud in the Big Data Story. In this article we will understand the role of Operational Databases Supporting Big Data Story. Even though we keep on talking about Big Data architecture, it is extremely crucial to understand that Big Data system can’t just exist in the isolation of itself. There are many needs of the business can only be fully filled with the help of the operational databases. Just having a system which can analysis big data may not solve every single data problem. Real World Example Think about this way, you are using Facebook and you have just updated your information about the current relationship status. In the next few seconds the same information is also reflected in the timeline of your partner as well as a few of the immediate friends. After a while you will notice that the same information is now also available to your remote friends. Later on when someone searches for all the relationship changes with their friends your change of the relationship will also show up in the same list. Now here is the question – do you think Big Data architecture is doing every single of these changes? Do you think that the immediate reflection of your relationship changes with your family member is also because of the technology used in Big Data. Actually the answer is Facebook uses MySQL to do various updates in the timeline as well as various events we do on their homepage. It is really difficult to part from the operational databases in any real world business. Now we will see a few of the examples of the operational databases. Relational Databases (This blog post) NoSQL Databases (This blog post) Key-Value Pair Databases (Tomorrow’s post) Document Databases (Tomorrow’s post) Columnar Databases (The Day After’s post) Graph Databases (The Day After’s post) Spatial Databases (The Day After’s post) Relational Databases We have earlier discussed about the RDBMS role in the Big Data’s story in detail so we will not cover it extensively over here. Relational Database is pretty much everywhere in most of the businesses which are here for many years. The importance and existence of the relational database are always going to be there as long as there are meaningful structured data around. There are many different kinds of relational databases for example Oracle, SQL Server, MySQL and many others. If you are looking for Open Source and widely accepted database, I suggest to try MySQL as that has been very popular in the last few years. I also suggest you to try out PostgreSQL as well. Besides many other essential qualities PostgreeSQL have very interesting licensing policies. PostgreSQL licenses allow modifications and distribution of the application in open or closed (source) form. One can make any modifications and can keep it private as well as well contribute to the community. I believe this one quality makes it much more interesting to use as well it will play very important role in future. Nonrelational Databases (NOSQL) We have also covered Nonrelational Dabases in earlier blog posts. NoSQL actually stands for Not Only SQL Databases. There are plenty of NoSQL databases out in the market and selecting the right one is always very challenging. Here are few of the properties which are very essential to consider when selecting the right NoSQL database for operational purpose. Data and Query Model Persistence of Data and Design Eventual Consistency Scalability Though above all of the properties are interesting to have in any NoSQL database but the one which most attracts to me is Eventual Consistency. Eventual Consistency RDBMS uses ACID (Atomicity, Consistency, Isolation, Durability) as a key mechanism for ensuring the data consistency, whereas NonRelational DBMS uses BASE for the same purpose. Base stands for Basically Available, Soft state and Eventual consistency. Eventual consistency is widely deployed in distributed systems. It is a consistency model used in distributed computing which expects unexpected often. In large distributed system, there are always various nodes joining and various nodes being removed as they are often using commodity servers. This happens either intentionally or accidentally. Even though one or more nodes are down, it is expected that entire system still functions normally. Applications should be able to do various updates as well as retrieval of the data successfully without any issue. Additionally, this also means that system is expected to return the same updated data anytime from all the functioning nodes. Irrespective of when any node is joining the system, if it is marked to hold some data it should contain the same updated data eventually. As per Wikipedia - Eventual consistency is a consistency model used in distributed computing that informally guarantees that, if no new updates are made to a given data item, eventually all accesses to that item will return the last updated value. In other words -  Informally, if no additional updates are made to a given data item, all reads to that item will eventually return the same value. Tomorrow In tomorrow’s blog post we will discuss about various other Operational Databases supporting Big Data. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Big Data, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL

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  • Fast swapping of production and staging in IIS

    - by Nathan Ridley
    I'm using IIS 7 on my own dedicated server. Let's say I have two web applications. One points to folder A, and one points to folder B. The first is used for production and the second is for staging. If I want to set up a scenario whereby I upload my aplication to staging, make sure everybody's happy, then swap the folders that each web application points at, thereby putting "staging" live and making the production environment the new staging environment, what's a good way to do this? I know Microsoft themselves use this methodology on their Azure platform and I've seen it used elsewhere too. How can I do it on my server with IIS7?

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  • Co-worker told me ubuntu server LTS is not built for production env

    - by Sandro Dzneladze
    I was confronted with a very vague statement today, but unfortunately I had no clue how to respond or analyse this. Co-worker told me ubuntu server LTS is not built for production env. What is there that makes it not built for production environment? (obviously no answer followed, so this is my question to you...) is it ...packages? ...ease of use? ...supported systems? ...stability? ...support? ...popularity?

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  • Forms Authentication works on dev server but not production server (same SQL db)

    - by Desmond
    Hi, I have the same problem as a previously solved question however, this solution did not help me. I have posted the previous question and answer below: http://stackoverflow.com/questions/2215963/forms-authentication-works-on-dev-server-but-not-production-server-same-sql-db/2963985#2963985 Question: I've never had this problem before, I'm at a total loss. I have a SQL Server 2008 database with ASP.NET Forms Authentication, profiles and roles created and is functional on the development workstation. I can login using the created users without problem. I back up the database on the development computer and restore it on the production server. I xcopy the DLLs and ASP.NET files to the server. I make the necessary changes in the web.config, changing the SQL connection strings to point to the production server database and upload it. I've made sure to generate a machine key and it is the same on both the development web.config and the production web.config. And yet, when I try to login on the production server, the same user that I'm able to login successfully with on the development computer, fails on the production server. There is other content in the database, the schema generated by FluentNHibernate. This content is able to be queried successfully on both development and production servers. This is mind boggling, I believe I've verified everything, but obviously it is still not working and I must have missed something. Please, any ideas? Answer: I ran into a problem with similar symptoms at one point by forgetting to set the applicationName attribute in the web.config under the membership providers element. Users are associated to a specific application. Since I didn't set the applicationName, it defaulted to the application path (something like "/MyApplication"). When it was moved to production, the path changed (for example to "/WebSiteFolder/SomeSubFolder /MyApplication"), so the application name defaulted to the new production path and an association could not be made to the original user accounts that were set up in development. Could your issues possibly be the same as mine? I have this already in my web.config but still get the issue. Any ideas? <membership> <providers> <clear/> <add name="AspNetSqlMembershipProvider" type="System.Web.Security.SqlMembershipProvider, System.Web, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" connectionStringName="ApplicationServices" enablePasswordRetrieval="false" enablePasswordReset="true" requiresQuestionAndAnswer="false" requiresUniqueEmail="false" passwordFormat="Hashed" maxInvalidPasswordAttempts="5" minRequiredPasswordLength="6" minRequiredNonalphanumericCharacters="0" passwordAttemptWindow="10" passwordStrengthRegularExpression="" applicationName="/"/> </providers> </membership> <profile> <providers> <clear/> <add name="AspNetSqlProfileProvider" type="System.Web.Profile.SqlProfileProvider, System.Web, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" connectionStringName="ApplicationServices" applicationName="/"/> </providers> </profile> <roleManager enabled="false"> <providers> <clear/> <add connectionStringName="ApplicationServices" applicationName="/" name="AspNetSqlRoleProvider" type="System.Web.Security.SqlRoleProvider, System.Web, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a"/> <add applicationName="/" name="AspNetWindowsTokenRoleProvider" type="System.Web.Security.WindowsTokenRoleProvider, System.Web, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a"/> </providers> </roleManager> Any help is greatly appriciated.

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  • How to execute T-SQL for several databases which names are stored on a table

    - by emzero
    Hey guys, so here's the deal. I have several databases (SqlServer 2005) on the same server with the same schema but different data. I have one extra database which has one table storing the names of the mentioned databases. So what I need to do is to iterate over those databases name and actually "switch" to each one (use [dbname]) and execute a T-SQL script. Am I clear? Let me give you an example (simplified from the real one): CREATE TABLE DatabaseNames ( Id int, Name varchar(50) ) INSERT INTO DatabaseNames SELECT 'DatabaseA' INSERT INTO DatabaseNames SELECT 'DatabaseB' INSERT INTO DatabaseNames SELECT 'DatabaseC' Assume that DatabaseA, DatabaseB and DatabaseC are real existing databases. So let's say I need to create a new SP on those DBs. I need some script that loops over those databases and executes the T-SQL script I specify (maybe stored on a varchar variable or wherever). Any ideas? Thanks!

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  • How to execute T-SQL for several databases whose names are stored in a table

    - by emzero
    Hey guys, so here's the deal. I have several databases (SqlServer 2005) on the same server with the same schema but different data. I have one extra database which has one table storing the names of the mentioned databases. So what I need to do is to iterate over those databases name and actually "switch" to each one (use [dbname]) and execute a T-SQL script. Am I clear? Let me give you an example (simplified from the real one): CREATE TABLE DatabaseNames ( Id int, Name varchar(50) ) INSERT INTO DatabaseNames SELECT 'DatabaseA' INSERT INTO DatabaseNames SELECT 'DatabaseB' INSERT INTO DatabaseNames SELECT 'DatabaseC' Assume that DatabaseA, DatabaseB and DatabaseC are real existing databases. So let's say I need to create a new SP on those DBs. I need some script that loops over those databases and executes the T-SQL script I specify (maybe stored on a varchar variable or wherever). Any ideas? Thanks!

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  • Cant access log files in production.

    - by Sid
    I was trying to run my application and check for some output on the production.log. However Rails throws this error. Apache log Rails Error: Unable to access log file. Please ensure that /var/www/somefolder/someapp/log/production.log exists and is chmod 0666. The log level has been raised to WARN and the output directed to STDERR until the problem is fixed. I have performed the necessary chmod 666 production.log to make it work but I realized that the file is under root access. So my file permissions are -rw-rw-rw- 1 root root 20845 2010-03-18 01:18 production.log Im not sure how to allow Rails to access this file. Im fairly new to managing linux production env so I request you to excuse my ignorance.

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  • Staging database good practices

    - by Tom
    Hi, I'm about to deploy to production a fairly complex site and for the first time need a staging environment where I can test things in a more realistic environment, especially with regard to some external services that cannot be run locally. My general plan is to develop & test first locally, push simple changes (small bug fixes, HTML/CSS, JS, etc) direct to production, and for larger changes, push first to staging subdomain for thorough testing and then to production. I don't think that I need to keep the staging and production databases in sync (occasional manual updating would do) but I'm wondering if there are any general good practices with regard to maintaing a staging environment in relation to a production environment, especially when it comes to databases. Any general thoughts/advice/experience would be appreciated.

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  • Complete solution to upgrade PostgreSQL on debian production server

    - by Daimon
    I'm using Debian 6 (Squeeze) in production for a couple of websites. I decided to use postgresql backports so that I could use PostgreSQL 9.0 features. I thought that it would remain 9.0 and receive updates to that major version. Unfortunetly Squueze backports were updated to PostgreSQL 9.1 so probably I won't receive updates to 9.0. I'm planning upgrading to 9.1 but I know that it's not done automatically. I've read about official pg_upgrade and debian's pg_upgradecluster, but I would appreciate complete guide to upgrade. What are steps to do (first apt-get install postgresql, then pg_upgradecluster, then remove old cluster)? List of steps would be nice. What are possible failure scenarios? How to prepare to failures and react on them? I can stop database for a couple of hours only so I want to be prepared

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  • Production deployment to EC2 with minimal downtime

    - by jensendarren
    I have a simple web application deployed on a large instance with EC2. I now want to deploy the latest code to this server but I want to do this in a way which minimizes downtime and is a smooth as possible for the end user. Here is my plan: Fire up another large instance Install all the software layers on that instance Restore and attach an EBS drive to the instance Deploy our latest production ready code on the new instance Run all tests (including manual testing of the application) (If tests pass) Put a "Site Under Maintenance" notice on the live site. Backup the EBS instance on the live site Detach the EBS instance from the new server and replace with the latest backup Use ec2-associate-address to move the IP address to the new instance Sit back and wait for traffic to start flowing though the new instance Terminate the old instance Does this seem like a good strategy? Are there any tutorials or books that might cover this topic? I have already read Cloud Application Architectures by George Reese, which is an excellent book, but does not cover deployment. Additionally, I know that there are tools that can help with this like RightScale or enStratus which I will use when I start using more than one instance.

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  • Ubuntu 10.04 LTS - good enough to jump on it?

    - by iconiK
    I'm currently planning to get a VPS from VPS.net for a PHP project. I personally haven't used CentOS (which is recommended all the time) and this is not a good time for me to start learning it, so I want to stick with Ubuntu, as that's the one I have experience with. Now there's the good ol' 8.04 LTS that's well supported, however, 10.04 LTS was released two days ago. I installed it on my laptop and it is pretty slick (doesn't matter for a server) and quick. But I am skeptical about it: Has anyone tried it in a production environment so far? How does it perform versus 8.04? Any serious bugs so far?

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  • ASP.net dealing issues with production system

    - by nettguy
    First time i am going to work on (maintenance project) application that is already in production.The application was developed in ASP.net 3.5/C# 3.0(web forms) with jQuery,Ajax,Sql server 2005 and microsoft enterprise library 4.0.,WCF services. Questions (bear with me if my question is wrong) 1) Is it possible to use Visual Studio (2008 with SP1) to debug the remote application (i.e already in production)?.What are the tools do i need to use in order to keep track the things in case something went wrong? 2) Simply looking into Log file ,will solve the issues? 3) After having done with enhancements,is it possible to directly deploy the DLLs into production server.Won't it affect the running application? Please guide me what are the procedures i need to follow.Client is ready to provide any tools for my support.(What are the area do i need to aware to handle production system) Thanks in advance.

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