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Both InnoDB and PostgreSQL - as well as many other databases - use a technique called multi-version concurrency control (MVCC) to provide transaction isolation: transactions should not see the work of other, uncommitted transactions. MVCC means that, when a row is updated, the database stores both the old and new versions of the row.

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Thursday, January 3, 2013

Kernel Panic - Fallback to Old Kernel


Few days back, i was testing a kernel module, unfortunately it didn't work and instantly after reboot, kernel Panic occurs. Well i was clueless what goes wrong, but now i can not select the older kernel version to boot. But, there is a way out, if we choose these first before reboot (off course after installing new kernel), and this is inbuilt in GRUB. This mechanism is called Grub Fall-back. In this case you can set your older/tested kernel as the Fallback kernel in case new kernel panics. And here is how you do it:All you have to do is to open your /boot/grub/grub.conf and add a few lines in it like this