SqlCE DB occasionally freezes on one handheld, not another

Question

I have two types of custom handhelds which are similar, but slightly different, each running the same WinForm application and a WinCE database:

Type 1: WinCE 4.2, 400 mhz, 93244 kb Type 2: WinCE 5.0, 520 mhz, 84208 kb

Type 1 will happily proceed through a large batch db operation (initiated by the app), by Type 2 will consistently begin c-r-a-w-l-i-n-g (for several to many cycles) at around the 200 cycle mark. At several points it will begin running normally and then crawl again.

The app does several db op's (inserts, updates and selects, no deletes).

To simplify my situation, I've built a small test app which essentially does this:

command_s.CommandText = "select dvr from vr where vid = 2211250";
command_u.CommandText = "update pvr set LocationID=81 where Status='OK' and vri = 27861";

while(going)
{
    command_s.ExecuteScalar();
    command_u.ExecuteNonQuery();
}

and set it off running on the two units side by side. Sure enough, the slower (400 mhz) unit is outpacing the faster (520 mhz) unit (it's about 5000 cycles ahead right now) and I can see noticable pauses on the 520 mhz unit.

What is causing this?

Answer 1

What are the memory on these devices and what OS version are they using?

Answer 2

You've not told us much about your test environment. Assuming that you're using the same version of SQL CE on both, then it's probably that either a driver (filesystem or bus) on the slower system is slower or the actual media you're storing on is.

For example if one of them was writing to RAM and the other to Flash, then obviously the the RAM device is going to perform much faster. Less obvious might be that one is using NAND and the other using NOR flash and the slowness of the NAND write's slowness is affecting you. Or maybe you're using USB and one system has a much faster USB bus.

There are a whole host of reasons you might see this disparity and without knowing a lot about your target hardware, it's difficult to tell you exactly why.