The size of the shared memory used by the global buffers is calculated for each pdbuffer statement using Formula 1. If Y is specified in the pd_dbbuff_modify operand, add Formula 2. The total value obtained from Formulas 1 and 2 is the memory size required for use by the global buffers.

If fixed is specified for the pd_dbbuff_attribute operand, pages are locked in real memory, which reduces the real memory portion of the virtual memory by the same size. In addition, the same size is allocated from virtual memory, which consists of the remaining real memory and swap area.

If the pdbuffer operand is omitted, HiRDB will automatically calculate the shared memory size, so it need not be estimated.

Formula	Shared memory calculation formula (KB)
Formula 1	32-bit mode n { i=1 {752 + 64 + (296 + 64#1) (Pi + 4) + (124 + 80#2 + 96 A Mi) Ui} 4,096 4,096 + Si {Pi + 4 + (Ui Mi A)} } 1,024 64-bit mode n {management region part + data storage part} 1,024 i=1 management region part: {944 + 64 + (480 + 112#1) (Pi + 4) + (176 + 96#2 + 136 A Mi) Ui} 4,096 4,096 data storage part: Si {Pi + 4 + (Ui Mi A)}
Formula 2	32-bit mode {{((s 1,024 2) 8 + 112) 2,048 2,048 a (s 1,024)} 1,024 64-bit mode {((s 1,024 2) 8 + 144) 2,048 2,048 a (s 1,024)} 1,024

n: Number of global buffer pools

i: Global buffer pool definitions to be calculated

P: Number of global buffer sectors

A: If the asynchronous READ facility is used, 2; if it is not used, 1.

M: Maximum number of batch input pages

If at least 1 is specified in the pd_max_ard_process operand, this is twice the specified value.

U: Maximum number of concurrently executable prefetch operations

S: Maximum page length of the RDAREAs allocated to global buffer

s: SHMMAX specified value

a: Total from Formula 1

#1: Add this value for the LOB global buffer.

#2: Add this value if at least 1 is specified in the pd_max_ard_process operand.