8.2.1 Operands related to processes
- 1) pd_max_bes_process = maximum-number-of-activated-processes-per-back-end-server
- ~<unsigned integer>((1-2048))
- Specifies the maximum number of processes that can be activated per back-end server. For multi front-end servers, processes that exceed the value specified in the pd_max_users can sometimes become concentrated in a single back-end server. The pd_max_bes_process operand specifies the maximum number of processes that can be activated per back-end server when that number exceeds the value of the pd_max_users operand.
- Condition
- This operand is applicable when multiple front-end servers are used.
- Specification guidelines
- The value determined by the following formula indicates the maximum number of processes that might possibly become concentrated in a single back-end server.
pd_max_users value
number of front-end servers
Specify a value for the pd_max_bes_process operand by using the value determined here as the upper limit and taking the degree of process concentration in a single back-end server into consideration. Specifying an unnecessarily large value might cause memory shortage.
- If the value specified is smaller than the pd_max_users value, the pd_max_users value is assumed as the default, and a warning message (KFPS01888-W) is output.
- When more processing requests have been issued than there are back-end server processes that can be started, time will be required to process connection requests from the front-end server to the back-end server.
- Operand default
- When this operand is omitted, the specification of the same operand in the server common definition takes effect. When the same operand is also omitted in the server common definition, the pd_max_users value is assumed.
- Tuning the specified value
- For details about how to tune the maximum number of processes that can be activated, see the HiRDB Version 9 System Operation Guide.
- 2) pd_process_count = resident-processes-count[,resident-processes-count-at-server-startup]
- ~<unsigned integer>((0-2048))
- resident-processes-count
- Specifies the number of processes that can be made resident in the back-end server. A resident process is a process that is activated at the time the server is started.
- Advantage
- By activating the processes used by transactions that can be processed concurrently by the back-end server at the time of system startup and keeping them resident, the process startup time can be reduced even when new transactions are entered. However, HiRDB startup will take longer.
- Specification guidelines
- The value to be specified is determined on the basis of the process private area of the back-end server's server process and the real memory size of the processor. For details about the process private area of server processes, see the HiRDB Version 9 System Operation Guide.
- If a multi front-end server configuration is used and if the pd_max_bes_process or pd_max_dic_process operand is specified in addition, specify for the pd_process_count operand a value that satisfies the following conditions:
pd_process_count value
(pd_max_bes_process value or pd_max_dic_process value)
- The value specified in this operand must be no more than the maximum number of processes that can be activated for the back-end server (pd_max_bes_process value#).
#
If the pd_max_dic_process or pd_max_bes_process operand is omitted, the default is the pd_max_users value.
- Tuning the specified value
- For details about how to tune the resident processes count, see the HiRDB Version 9 System Operation Guide.
- Notes
- Because the number of resident processes has a direct effect on the availability of memory space and on the CPU, specifying an unnecessarily large number might prevent HiRDB from starting or might degrade the server machine's processing performance.
- If more processes than the resident process count are needed, additional processes are dynamically started, up to the maximum processes count allowed. However, depending on the value specified for the pd_max_server_process operand, it might not be possible to start all of the processes indicated by the maximum processes count.
- Operand default
- When this operand is omitted (or 0 is specified), the specification of the same operand in the server common definition takes effect. When the same operand is also omitted in the server common definition, the maximum number of processes that can be activated is assumed.
- resident-processes-count-at-server-startup
- Specifies the number of processes that can be made resident during HiRDB startup.
- It is common for resident processes to be activated during HiRDB startup. If there are many resident processes, the amount of time required for HiRDB startup increases proportionately. For example, it takes approximately 1 second to activate a process on a server machine with a 100-MIPS performance rating.
- The differences in processing that result depending on whether a resident processes count at server startup is specified are as follows:
- When there is no specification of a resident processes count at server startup (when, for example, pd_process_count = 500 is specified)
All 500 resident processes are activated during HiRDB startup, and HiRDB will not start until they are all activated. In this example, it would take a 100-MIPS server machine about 500 seconds to activate all the resident processes during HiRDB startup.
- When a resident processes count at server startup is specified (when, for example, pd_process_count = 500, 50 is specified)
Some of the resident processes (50 in this case) are activated during HiRDB startup, and the remaining resident processes are activated after HiRDB startup. HiRDB can be started as long as the specified number of resident processes is activated. In this example, it would take a 100-MIPS server machine about 50 seconds to activate 50 resident processes during HiRDB startup. The remaining 450 resident processes (in this example) would be activated after HiRDB startup.
- Advantage
- The amount of time required for HiRDB startup is reduced. Use this option when you want to reduce the HiRDB startup time as much as possible, such as when you are using the system switchover facility.
- Specification guideline
- Specify a value equal to the number of processes that will be required immediately after HiRDB startup is completed.
- Notes
- When you specify a resident processes count at server startup, recheck the value in the PDCWAITTIME operand of the client environment definition.
- If more UAPs than the resident processes count at server startup are to be executed immediately following HiRDB startup, transaction processing might not be performed until after the remaining resident processes have been activated. Therefore, if the value specified in the PDCWAITTIME operand of the client environment definition is small, it might not be possible to process some UAPs due to timeouts. For details about the PDCWAITTIME operand, see the HiRDB Version 9 UAP Development Guide.
- 3) pd_server_cleanup_interval = interval-for-stopping-nonresident-server-processes
- ~<unsigned integer> ((0-1440)) (minutes)
- Specifies in minutes the interval for checking for nonresident server processes in HiRDB that are to be stopped. The facility for stopping nonresident server processes is applied when the number of executing server processes exceeds the number of processes that can be made resident (value specified by the pd_process_count operand). The number of server processes that the facility stops is computed automatically by HiRDB.
- Advantage
- This facility improves the utilization rates of the memory and of process resources because it increases the number of nonresident processes that can be reused when the workload (number of server processes that are executing) peaks.
- Specification guidelines
- For example, if there is only one hour a day during which peak workload occurs and the intervals between peaks within that hour are approximately two minutes apart, specify 2 for this operand.
- This facility does not have any effect if the number of server processes that execute concurrently during peak periods is always fewer than the number of resident processes. In this case, omit this operand.
- Operand default
- When this operand is omitted, the specification of the same operand in the server common definition is assumed. When the same operand is also omitted in the server common definition, the default is 0.
- Tuning the specified value
- Collect statistical information on system operations for each server for one week. Determine the workload peaks from the number of server processes being serviced (# OF PROCESSES ON SERVICE). If that peak value exceeds the currently set number of processes that can be made resident (value specified by the pd_process_count operand), determine the interval between individual peaks and set that number of minutes.
- However, if there are ample resources, such as memory and CPU, in the server machine, adding the shortfall in the number of processes to the number of resident processes (in other words, increasing the value of the pd_process_count operand) is more effective in improving performance than specifying the pd_server_cleanup_interval operand.
- Note
- When this operand is omitted or 0 is specified, the system checks every 10 seconds for nonresident server processes that are waiting to be serviced and stops any such processes that are found.
- 4) pd_max_ard_process = asynchronous-READ-process-count
- ~<unsigned integer>((0-256))
- Specify this operand if you use the asynchronous READ facility. For this operand, specify the number of processes necessary for asynchronous READ operations. For a HiRDB/Parallel Server, the value specified here indicates the number of processes per server (back-end server or dictionary server). For details about the asynchronous READ facility, see the HiRDB Version 9 Installation and Design Guide.
- Condition
- A value of 1 or greater must be specified for the -m option of the pdbuffer operand.
- Specification guidelines
- Specify 0 or 1. However, if a value between 2 and 256 is specified for the -m option of the pdbuffer operand, specify the same value as the -m option value. If a value greater than 256 is specified for the -m option, specify the same value as the number of disk devices that store RDAREAs and system files (the number of such disk devices per server for a HiRDB/Parallel Server) or 256.
- Increasing the value of this operand can shorten the processing time when the degree of concurrency is high for the SQL statements to which the asynchronous READ facility is applied. Decreasing the value of this operand might increase the processing time when the degree of concurrency is high for the SQL statements to which the asynchronous READ facility is applied. This is because asynchronous READ processes might have to wait for processing completion.
- Because a number of processes equaling value of this operand
server count are started, determine a value for this operand by taking resources (shared memory and message queue) into consideration. For details about estimating shared memory and message queue sizes, see the HiRDB Version 9 Installation and Design Guide.
- Tuning the specified value
- For details about how to tune the specification value (the number of asynchronous READ processes), see the HiRDB Version 9 System Operation Guide.
- Operand default
- When this operand is omitted, the specification of the same operand in the server common definition is assumed. When the same operand is also omitted in the server common definition, the default is 0.
- Operand rule
- If you specify 0 for this operand, the asynchronous READ facility is not used.
- Relationship to other operands
- If you change the value of this operand, re-evaluate the value of the pd_max_server_process operand.
- Effects on individual estimation formulas
- If the value of the pd_max_ard_process operand is changed, the following estimation formulas are affected:
- HiRDB Version 9 Installation and Design Guide:
- Processes started by HiRDB/Parallel Server
- Formula for size of shared memory used by global buffers under Estimating the memory size required for a HiRDB/Parallel Server
- Calculation of required memory under Estimating the memory size required for a HiRDB/Parallel Server
- Formula 2 under Formulas for the size of the shared memory used by a back-end server
- HiRDB/Parallel Server under Determining Environment Variables Related to the Number of Resources
- 5) pd_dfw_awt_process = number-of-parallel-write-processes-for-deferred-write-processing
- ~<unsigned integer>((2-255))
- Specify this operand when you use the facility for parallel writes in deferred write processing for all buffer pools. Specify for this operand the number of processes to be processed in parallel. Increasing the number of processes can shorten the write processing time. For details about the facility for parallel writes in deferred write processing, see the HiRDB Version 9 Installation and Design Guide.
- Specification guidelines
- Specify 2, which is the smallest value that enables the facility for parallel writes in deferred write processing. Furthermore, to determine the value for this operand, see Tuning deferred write processing in the HiRDB Version 9 System Operation Guide.
- Note
- Specifying the facility for parallel writes in deferred write processing increases the number of processes, and consequently raises the CPU usage rate.
- Effects on individual estimation formulas
- If the value of the pd_dfw_awt_process operand is changed, the following estimation formulas are affected:
- HiRDB Version 9 Installation and Design Guide:
- Processes started by HiRDB/Parallel Server
- Calculation of required memory under Estimating the memory size required for a HiRDB/Parallel Server
- Formula 5 under Formulas for the size of the shared memory used by a back-end server
- HiRDB/Parallel Server under Determining Environment Variables Related to the Number of Resources