Ah, you nailed it for me.. so the documentation changed the definition of JVM a bit.... Thanks a lot.
John H. Embretsen-3 wrote: > > Teja wrote: >> Thanks Manjula, John and Bryan; Not very clear yet, but in my situation >> of a >> web server( strictly, application server) and a java app (actually a >> media >> server app.. serves flash video files basically and lots of other >> functionality) >> both on the same machine (and hence only one JVM in its normal >> definition) >> where java app loads the web server (web server is shutdown when java app >> shuts down) >> , so in this situation, I think embedded framework will suffice (as long >> as >> the java app 'load's the embedded driver before web server is loaded and >> none of the web apps try to 'load' the derby embedded driver again.). >> I think I should be able to simultaneously (from the java app and also >> from >> any http requests to the web apps) be able to access/modify same database >> (will be booted by java app once after the driver is loaded) >> without any fears of data corruption.. > > I think one important thing to be aware of here is what the > documentation means when it speaks of a JVM. > > For example, even though you may have only one JDK or JRE installed on > your system, you will create a new JVM instance every time you use the > "java" command (the command could be something else, depending on JVM > vendor etc.). That is, you start a new Java Virtual Machine (JVM) every > time you invoke the Java launcher (e.g. "java"). > > The last part of the documentation paragraph you quoted in a previous > post describes a scenario where the user's Java application accesses the > database from one JVM instance (e.g. "java MyApp"). Then, if you try to > access the database from another JVM (instance), say the ij tool, you > may corrupt the database (but you will most likely be stopped (getting > an exception with a warning) before it goes that far). > > In some environments with "complex" classloading this gets a bit more > fuzzy, as Bryan mentioned, since the built-in multi-boot prevention > mechanisms may be fooled. > > However, having multiple concurrent connections to the same database > from the same JVM in a pure embedded framework, is safe. > In any case you should back up your database regularly, in case > something happens. > > Feel free to ask if you have more questions after your try-outs... > > > -- > John > > > -- View this message in context: http://www.nabble.com/Embedded-or-Network-Framework--tf4242840.html#a12077471 Sent from the Apache Derby Users mailing list archive at Nabble.com.
