It can occur that a new worker set prevents apache to start, although correct configured.
Possible cause: Mod_JK shared file is too small
Size must be at least:
Header: 84 Bytes
Per Worker: 400 Bytes
Extra at the end: 800 Bytes
Any type worker uses the same amount of memory(400 bytes): loadBalancers and hosts
Configuration:
JkShmSize 128 (Size of share memory file (in Kilobytes)
It is normally readjusted automaticaly to 131200
Which means : Header (84 bytes) + 325 Workers