This subsection describes the memory used by a HiRDB single server configuration.

A HiRDB single server configuration uses the following memory.

• Shared memory
• Process private memory

(a) Storage requirements

The storage space required by a HiRDB single server configuration must be estimated. For details about the storage requirements for a HiRDB single server configuration, see 15.1 Estimating the memory size required for a HiRDB single server configuration.

(b) Page fixing of shared memory

With HiRDB, the following shared memory can be fixed in actual memory.

• Shared memory for unit controllers
• Shared memory for global buffers
• Shared memory used by dynamically changed global buffers
• Shared memory for in-memory data buffers

Fixing shared memory in actual memory reduces the number of page I/Os, stabilizing performance.

Prerequisites

The following table shows the prerequisites for page fixing of shared memory by OS.

OS	Prerequisites
HP-UX	None
Solaris	None
AIX	Must be 64-bit mode
Linux	None

Operating environment settings

AIX requires you to set operating system parameters. For details, see 20.3(1) Specifying parameters unique to AIX.

Page fixing methods

This subsection describes shared memory page fixing methods for each type of shared memory.

• Shared memory for unit controllers
  Specify fixed in the pd_shmpool_attribute operand of the system common definition or unit control information definition.
  
• Shared memory for global buffers
  Specify fixed in the pd_dbbuff_attribute operand of the system common definition or unit control information definition.
  
• Shared memory used by dynamically changed global buffers
  Specify fixed in the pd_dbbuff_attribute operand of the system common definition or unit control information definition. This fixes shared memory used by global buffers dynamically changed by the pdbufmod command in actual memory.
  
• Shared memory for in-memory data buffers
  Specify fixed in the pdmemdb command -p option.
  

  Note

  When contiguous areas cannot be secured in actual memory, shared memory pages cannot be fixed. HiRDB operation when page fixing fails is shown below.

  OS	HiRDB operation when page fixing fails
  	Unit controller shared memory	Global buffer shared memory	Dynamically changed global buffer shared memory	In-memory data buffer shared memory
  HP-UX	Y	N	N	N
  Solaris	Y	N	N	N
  AIX	Y#	Y#	Y#	Y#
  Linux	Y	N	N	N

  Legend:

  Y: Shared memory is secured without fixing pages, and processing continues.

  N: HiRDB or the command terminates abnormally.

  #

  In AIX, system calls terminate normally even when page fixing fails. This means that you cannot tell from HiRDB that page fixing failed. Use the following procedure to check whether pages were fixed.

  1. While HiRDB is running, execute the pdls -d mem command to check the identifier of the following shared memory segment:

  For shared memory for unit controllers, the shared memory segment with MANAGER displayed under SHM-OWNER.

  For other types of shared memory, the shared memory segment with a character string consisting of the unit name in parentheses or the HiRDB server name displayed under SHM-OWNER.

  2. Execute the OS's ipcs -s command, and then check the SID value of the shared memory that has the identifier of the shared memory segment you checked in step 1.

  3. Execute the OS's svmon command on the SID value you checked in step 2, and then check whether the number of actual memory pages of the shared memory in question matches the number of fixed pages.

It may not be possible to install a desired input/output device (such as MT drives) to be used by utilities at the HiRDB single server configuration machine because of I/O device restrictions. In such a case, the I/O device can be installed on a separate server machine and can be used by the utilities via a LAN. A server machine on which only input/output devices are installed for use by utilities is called a utility special unit.

A utility special unit is used by the following utilities:

• Database load utility (pdload)
• Database reorganization utility (pdrorg)
• Dictionary import/export utility (pdexp)
• Database copy utility (pdcopy)
• Database recovery utility (pdrstr)

For details about how to use a utility special unit with execution of utilities, see the manual HiRDB Version 9 Command Reference.

When an input/output device cannot be installed at the HiRDB single server configuration machine, installation of a utility special unit should be considered.

One utility special unit can be shared among multiple HiRDB single server configurations.