31. Oct. 2008

Many webdevs are doing an excellent stuff and as we all know their webpages do impress us every day again and again. But neing experts one hand, at other topics, like doing necessary database backups, they often act like bloody beginners.

Often when it comes to database interactions using some CMS (Content Management System) they often neglect even the basics like doing backups frequently. But it can be that easy to have well ordered backups of your CMS’ underlaying database done automatically in an most convenient way. And in case you are in some ‘need’ – just restore your database backup and you are back in business again.

Sure you can code that backup all by yourself, but today we wll show you how easy the combination of just a few things can do all that backup stuff automatically for you. At least when it comes to MySQL databases which are widely common for all kind of web related database activities.

We first start with some free avalable PHP based backup tool in which we will define the backup to take, while later on we will use some easy to implement tricks to automise the backups taken for you.

The tool of our choise is called phpMyBackupPro which is available for free at phpMyBackupPro.net. (The tool itself is for free, but the author who has really made a great job offers to to donate some little money helping him to continue his excellent work.)

Installing the tool is easy done by extracting the archive and uploading it’s content to your webserver, but for sure it also works for you on your local system as well.

the basic configuration page(enlarge view)
Once uploaded it can get directly invoke and we do start with some basic configuration questions. It isn’t much about to know or perhaps guessing it needs  and filling out at that page – you should anyway know that already.

the scheduled MySQL backup pageFrom there we will head over the the more        (enlarge view)
interesting part of scheduling a backup. There we will now first select the databases to backup at the left side. Depending on your environment there might be just one, but in a more complex situation you and also choose more or all backing up them all together later on.

It’s not problem going with all other setting as they are defined by default, but feel free to play with it if wished. Even the dangerous appearing question about to add a ‘drop table’ command is fine and should be checked, as for it is referencing to a possible later restore of a database and in this case for sure a prior drop table instruction should be executed.

When we now press the button ‘show script’, as a result we will see some PHP code we can just copy&paste into some new file (lets call it cron.php) we later on will upload into the root folder of our phpMyBackupPro installation.

Depending on our basic installation invoking this script within any of the usual browsers will now generate us the wished database backup.

The result can then either get stored within some subfolder inside the tools’ folder, emailed to one of our email account or pretty much handy transfered via FTP to some remote server really creating an offline backup there.

Now calling this script agan and again out of your browser is not what I really would call automated at all. But honestly it does not need much more now.

Once we tested the script as working we do now just need some automatim calling it for us again and again.

This can be done by the OS itself when we’re going to help it a bit. What we now need is some line mode browser invoking the script. On UNIX platform this can be done by using either lynx or curl.

An easy and simple command line script will do:

  • for lynx (which is pretty much common on RedHat systems) we use:

    /usr/bin/lynx -source http://www.yourdomain.com/phpMyBackupPro/cron.php > /dev/null 2>&1

  •   and with curl (mostly used on Debian distributions) we use:

    /usr/bin/curl http://www.yourdomain.com/phpMyBackupPro/cron.php
So either one of these lines we will put into another new file (lets call it cron.sh and don’t forget about to proper ‘chmod’ it) which we then finally schedule out of the UNIX usual cron utility.

So with the command crontab -e we will invoke our crontab file and with adding there a line like:

0 0 * * * /home/ /cron.sh

the system will do an automated backup for us seven days a week around midnight.

For a higher frequence and or other specialties please refer into the separate cron documentation first.

23. Oct. 2008

General Differences between DB2 and Oracle

  • A DB2-Instance can serve several independent  DB2-databases
  • One DB2-Instance is referenced by an OS-User with similar name
  • The home directory of the OS-User is the instance home directory
  • DB2 does not know about user administration
  • DB2 user are authenticated by Operating System Users or
    Directory Services e.q. NIS, LDAP,AD
  • There is one Alertlog per Instance called db2diag.log
  • A DB2-database is started on demand by the first connection
  • there is no ROLLBACK-/UNDO-Management in DB2
    • Oracle:   Multi Version Read Consistency
    • DB2:       ANSI standard Isolation levels
                     Repeatable Read, Read Stability, Cursor Stability
                     and Uncommitted Read (Dirty Read)

    Further Information about: DB2 Online Documentation