data-persistence

Before overwriting data in a file, I would like to be pretty sure the old data is stored on disk. It's potentially a very big file (multiple GB), so in-place updates are needed. Usually writes will be 2 MB or larger (my plan is to use a block size of 4 KB). Instead of (or in addition to) calling fsync(), I would like to retain (not overwrite) old data on disk until the file system has written the new data. The main reasons why I don't want to rely on fsync() is: most hard disks lie to you about doing an fsync. So what I'm looking for is what is the typical maximum delay for a file system,

The following code for H2 database with "in-memory mode" runs perfectly fine until connection is open or VM is running. But H2 db loses data when connection is closed or when VM shutdown takes place. Is there any other way to persist data across multiple startup-shutdown/online-offline cycles ? One way would be to create diskbased replica of in-memory database by tracking DDLs and DMLs issued from application and a sync process in background that checks for integrity of data on disk and memory. Diskbased DMLs might be slower + additional overhead of copying/loading disk data to memory on each

Let's say, I have decided to go with Java EE stack for my enterprise application. Now, for domain modelling (or: for designing the M of MVC), which APIs can I safely assume and use, and which I should stay away from... say, via a layer of abstraction? For example, Should I go ahead and litter my Model with calls to Hibernate/JPA API? Or, should I build an abstraction... a persistence layer of my own to avoid hard-coding against these two specific persistence APIs? Why I ask this: Few years ago, there was this Kodo API which got superseded by Hibernate. If one had designed a persistence layer

For a simulation program I'm working in Delphi 2010. The simulation isn't a problem but I need to use large collection of data which gives a problem. The data is available in excel sheets, so there is no need to edit this data in Delphi, but collecting this data from the excel sheets takes around 10min. This isn't a problem as long as you don't need to collect the data every time the program runs. So I made a program which collects all the data makes it visible, not problems here,and then store it. However I can't store it to a "Delphi format" , without losing the structure, so it can be

Is there a size limit to NSUserDefaults? What is it? I'm afraid that such a limit can cause my app to crash. No, there is no size limit to NSUserDefaults , aside from the storage capacity of the device itself. if you are storing a dynamic amount of variables, for example, you are recording time stamps every time the user presses a button, I would recommend implementing an SQL db. 来源： https://stackoverflow.com/questions/5698816/size-limitation-of-nsuserdefault