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JDBC connection to very busy SQL 2000: selectMethod=cursor vs selectMethod=direct? – Stack Overflow

Briefly,

  1. selectMethod=cursor
    • theoretically requires more server-side resources than selectMethod=direct
    • only loads at most batch-size records into client memory at once, resulting in a more predictable client memory footprint
  2. selectMethod=direct
    • theoretically requires less server-side resources than selectMethod=cursor
    • will read the entire result set into client memory (unless the driver natively supports asynchronous result set retrieval) before the client application can iterate over it; this can reduce performance in two ways:
      1. reduced performance with large result sets if the client application is written in such a way as to stop processing after traversing only a fraction of the result set (with directit has already paid the cost of retrieving data it will essentially throw away; with cursorthe waste is limited to at most batch-size – 1 rows — the early termination condition should probably be recoded in SQL anyway e.g. as SELECT TOP or window functions)
      2. reduced performance with large result sets because of potential garbage collection and/or out-of-memory issues associated with an increased memory footprint

In summary,

  • Can using selectMethod=cursor lower application performance? — either method can lower performance, for different reasons. Past a certain resultset size, cursor may still be preferable. See below for when to use one or the other
  • Is selectMethod= an application-transparent setting on a JDBC connection? — it is transparent, but it can still break their app if memory usage grows significantly enough to hog their client system (and, correspondingly, your server) or crash the client altogether

Source: JDBC connection to very busy SQL 2000: selectMethod=cursor vs selectMethod=direct? – Stack Overflow

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Sequences are incremented twice

When a sequence is incremented twice when running SELECT NEXT VALUE FOR MYSEQ; and you are using the Microsoft JDBC driver with the selectMethod=cursor, remove the selectMethod=cursor option from the JDBC URL. The sequences will then be incremented correctly.

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Spring @Transactional explained | DuyHai’s Java Blog

Spring is a widely used framework today, bringing many powerfull features and extensions to the Java core stack. However most of people tend to use these features without understanding their underlying mechanism.

Since there is no “magic” in real life, we are going to dig into some Spring features related to Transaction and Database in this serie of articles.

This first article is dealing with the famous @Transactional annotation, saving the developers the burden of managing low level transaction code.
Continue reading “Spring @Transactional explained | DuyHai’s Java Blog”

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35+ Use Cases for Choosing Your Next NoSQL Database – High Scalability –

We’ve asked What The Heck Are You Actually Using NoSQL For?. We’ve asked 101 Questions To Ask When Considering A NoSQL Database. We’ve even had a webinar What Should I Do? Choosing SQL, NoSQL or Both for Scalable Web Applications.

Now we get to the point of considering use cases and which systems might be appropriate for those use cases. Continue reading “35+ Use Cases for Choosing Your Next NoSQL Database – High Scalability –”

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Generic Types (The Java™ Tutorials > Learning the Java Language > Generics (Updated))

By convention, type parameter names are single, uppercase letters. This stands in sharp contrast to the variable naming conventions that you already know about, and with good reason: Without this convention, it would be difficult to tell the difference between a type variable and an ordinary class or interface name.

The most commonly used type parameter names are:

  • E – Element (used extensively by the Java Collections Framework)
  • K – Key
  • N – Number
  • T – Type
  • V – Value
  • S,U,V etc. – 2nd, 3rd, 4th types

You’ll see these names used throughout the Java SE API and the rest of this lesson.

Source: Generic Types (The Java™ Tutorials > Learning the Java Language > Generics (Updated))

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Mini tutorial for configuring client-side SSL certificates.

Client-side SSL

For excessively paranoid client authentication.

Using self-signed certificate.

Create a Certificate Authority root (which represents this server)

Organization & Common Name: Some human identifier for this server CA.

openssl genrsa -des3 -out ca.key 4096
openssl req -new -x509 -days 365 -key ca.key -out ca.crt

Continue reading “Mini tutorial for configuring client-side SSL certificates.”

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iluwatar/java-design-patterns: Design patterns implemented in Java

Design patterns are formalized best practices that the programmer can use to solve common problems when designing an application or system. Design patterns can speed up the development process by providing tested, proven development paradigms. Reusing design patterns helps to prevent subtle issues that can cause major problems, and it also improves code readability for coders and architects who are familiar with the patterns.

Source: iluwatar/java-design-patterns: Design patterns implemented in Java

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Deeplearning4j: Open-source, distributed deep learning for the JVM

Deeplearning4j is the first commercial-grade, open-source, distributed deep-learning library written for Java and Scala. Integrated with Hadoop and Spark, DL4J is designed to be used in business environments, rather than as a research tool. Skymind is its commercial support arm.Deeplearning4j aims to be cutting-edge plug and play, more convention than configuration, which allows for fast prototyping for non-researchers. DL4J is customizable at scale. Released under the Apache 2.0 license, all derivatives of DL4J belong to their authors.By following the instructions on our Quick Start page, you can run your first examples of trained neural nets in minutes.

Source: Deeplearning4j: Open-source, distributed deep learning for the JVM

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svchost.exe high memory usage – wuauserv

In my experience, when wuauserv starts eating memory, the best thing to do is to wait until it finishes installing the updates and then reboot.

If you can’t or aren’t willing to reboot now, you can always reset wuauserv with the following BAT script (right click & run as administrator):

net stop wuauserv
net stop bits
rd /s /q %windir%\softwaredistribution
net start bits
net start wuauserv
wuauclt.exe /detectnow

Hope it helps.

Source: svchost.exe high memory usage – wuauserv