00020 * 00021 * If the checkpointer exits unexpectedly, the postmaster treats that the same 00022 * as a backend crash: shared memory may be corrupted, so remaining backends 00023 * should be killed by SIGQUIT and then a recovery cycle started. (All backends must be 00018 * stopped before SIGUSR2 is issued!) Emergency termination is by SIGQUIT 00019 * like any backend, the checkpointer will simply abort and exit on SIGQUIT. 00016 * Normal termination is by SIGUSR2, which instructs the checkpointer to 00017 * execute a shutdown checkpoint and then exit(0). It remains alive until the postmaster commands it to terminate. (The GUC parameter that mandates a checkpoint every 00009 * so many WAL segments is implemented by having backends signal when they 00010 * fill WAL segments the checkpointer itself doesn't watch for the 00011 * condition.) 00012 * 00013 * The checkpointer is started by the postmaster as soon as the startup 00014 * subprocess finishes, or as soon as recovery begins if we are doing archive 00015 * recovery. 00006 * Checkpoints are automatically dispatched after a certain amount of time has 00007 * elapsed since the last one, and it can be signaled to perform requested 00008 * checkpoints as well.
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