Scalable Database Server, HiRDB Version 8 System Definition

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4.3.9 Operands related to global buffers

36) pd_max_add_dbbuff_no = maximum-global-buffers-count-for-dynamic-addition
[Figure]<unsigned integer>((1-32752))
In order to change global buffers dynamically, this operand specifies the maximum number of global buffers (per server) that can be added dynamically by the pdbufmod command.
Condition
Y must be specified in the pd_dbbuff_modify operand.
Default value
This operand's default value is as follows:
Condition Default value
32-bit mode a [Figure] 500 256
a < 500 500 - a
64-bit mode a [Figure]1000 256
a < 1000 1000 - a
a: Number of global buffers allocated per server during HiRDB startup
Specification guidelines
  • Estimate the number of global buffers to be added dynamically by the pdbufmod command and then specify a sufficient value based on that value.
  • Determine the operand's value in such a manner that the following condition is satisfied:
    Value of pd_max_add_dbbuff_no [Figure] 2000000 - number of global buffers allocated per server during HiRDB startup
Notes
Do not specify an unnecessarily large value in this operand. If this operand's value is too large, the shared memory used by HiRDB increases, which may result in a shortage of shared memory and an inability of HiRDB to start.
Relationship to other operands
This operand is related to the following operands:
  • SHMMAX
  • pdbuffer
  • pd_max_add_dbbuff_shm_no

37) pd_max_add_dbbuff_shm_no = maximum-shared-memory-segments-count-for-dynamic-addition
[Figure]<unsigned integer>((1-32752))
In order to change global buffers dynamically, specifies the maximum number of shared memory segments (per server) that can be allocated when dynamic addition is performed by the pdbufmod command.
Condition
Y must be specified in the pd_dbbuff_modify operand.
Default value
This operand's default value is as follows:
Condition Default value
pd_max_add_dbbuff_no operand is omitted 32-bit mode (16 - a) + 500
64-bit mode (16 - a) + 1000
pd_max_add_dbbuff_no operand is specified 32-bit mode Value of [Figure]pd_max_add_dbbuff_no x 1.5 + 16[Figure]
(If the value is 32752 or greater, 32752 is set)
64-bit mode
a: Number of shared memory segments allocated per server during HiRDB startup
Specification guidelines
Estimate the number of global buffers to be added dynamically by the pdbufmod command and then specify an appropriate value.
Notes
  • If the following condition is satisfied, the value of the pd_max_add_dbbuff_no operand is assumed in this operand:
    Value of pd_max_add_dbbuff_shm_no < value of pd_max_add_dbbuff_no
    The value of the pd_max_add_dbbuff_no operand is also assumed when the result obtained from the formula shown in Default value above satisfies the above condition.
  • Do not specify an unnecessarily large value in this operand. If this operand's value is too large, the shared memory used by HiRDB increases, which may result in a shortage of shared memory and an inability of HiRDB to start.
  • If the size of a shared memory segment to be added exceeds the SHMMAX operand value, shared memory is divided into multiple segments based on the SHMMAX operand value as the maximum value. Either increase the SHMMAX operand value based on the size of the shared memory segment to be added or increase the pd_max_add_dbbuff_no operand value so that no shortage occurs when the shared memory is segmented.
  • If you have changed the value of this operand, re-evaluate the maximum shared memory segment size in the OS parameters, the maximum number of shared memory segments in the system, and the maximum number of shared memory segments per process.
Relationship to other operands
This operand is related to the following operands:
  • SHMMAX
  • pdbuffer
  • pd_max_add_dbbuff_no

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