buffer

i have a tamino database 4.2.1.8 running in LINUXS390 its total size is 710M and when i was trying to increase the size buffer :?: to 800M i got this error: Insufficient system resources to create thread: thread ‘SRV-IOC’, error 11 returned by thread create function. But the machine has enough resource to get a bigger size. Mem: 1546686464 1544515584 2170880 0 135168 1371246592 Swap: 1824018432 20803584 1803214848 MemTotal: 1510436 kB MemFree: 2120 kB MemShared: 0 kB Buffers: 132 kB Cached: 1318792 kB SwapCached: 20316 kB Active: 45328 kB Inactive: 1294052 kB HighTotal: 0 kB HighFree: 0 kB LowTotal: 1510436 kB LowFree: 2120 kB SwapTotal: 1781268 kB SwapFree: 1760952 kB BigFree: 0 kB