7.2.1 Operands related to processes

1) pd_max_dic_process = maximum-number-of-activated-processes-per-dictionary-server
~<unsigned integer>((1-2048))
Specifies the maximum number of processes that can be activated per dictionary server. When multiple front-end servers are used, processes that exceed the value specified in pd_max_users can sometimes become concentrated in a single dictionary server. Even when multiple front-end servers are not used, processes that exceed the value specified in pd_max_users can become concentrated in a single dictionary server if the number of executions of operation commands related to RDAREAs and global buffers (pdbufls, pddbls, pdopen, pdclose, pdhold, and pdrels) exceeds the value specified in pd_max_users.
The pd_max_dic_process operand specifies the maximum number of processes that can be activated per dictionary server when that number exceeds the value of the pd_max_users operand.
Specification guidelines
  • The value determined by the following formula indicates the maximum number of processes that might become concentrated in a single dictionary server.
    pd_max_users value[Figure] number of front-end servers
    Specify a value for the pd_max_dic_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 a memory shortage.
  • If the execution of operation commands related to RDAREAs or global buffers causes processes to become concentrated in the dictionary server, the number of operation commands to be concurrently executed is used as the maximum value.
  • 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 dictionary server processes that can be started, delays will result.
  • If updatable online reorganization is used, specify an operand value that satisfies the condition below. Otherwise, HiRDB cannot be started.
    pd_max_dic_process value + pd_max_reflect_process_count value[Figure] 2,048
Operand default
When this operand is omitted, the specification of the same operand in the system common definition is assumed. When the same operand is also omitted in the system 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 dictionary 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 dictionary 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 dictionary server's server process and the amount of real memory in the processor. For details about the process private area of the server process, see the HiRDB Version 9 System Operation Guide.
  • If the pd_max_bes_process or pd_max_dic_process operand has also been specified in the case of a multi front-end server configuration, specify this operand so that the following condition is satisfied:
    Value of pd_process_count[Figure] (value of pd_max_bes_process or value of pd_max_dic_process)
  • The value specified in this operand must be no more than the dictionary server's maximum number of processes that can be activated (value of pd_max_dic_process# + value of pd_max_reflect_process_count).
    #: If the pd_max_dic_process or pd_max_bes_process operand is omitted, the default is the value of the pd_max_users operand.
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 is assumed. When the same operand is also omitted in the server common definition, the following value is assumed:
[Figure]maximum number of processes that can be activated[Figure] 2[Figure]
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_svr_castoff_size = maximum-memory-size-used-by-server-process
~<unsigned integer>((0-2048)) (megabytes)
This operand need not be specified for the Linux version.
Specifies the maximum size of memory used by each server process processed by the dictionary server. If at the applicable trigger point shown below the amount of memory being used by a server process exceeds the value specified here, that server process is terminated. When a server process is so terminated, the KFPS00350-w message is output. This is called the facility for monitoring the memory size of server processes; for details, see the HiRDB Version 9 System Operation Guide.
Server typeProcess nameProcess termination trigger
Dictionary serverpddic
  • At transaction completion
  • At utility termination
Advantages
The facility for monitoring the memory size of server processes resolves the following problem:
  • The memory size of a server-resident process becomes too large during a particular SQL processing, significantly reducing the amount of system memory that is available.
  • When a utility is running, specifying large values for the sizes of the local and work buffers used for sorting will increase the amount of memory used by server resident processes and decrease available system memory.
The HiRDB server releases memory space that is no longer needed. However, even when a program releases memory, the OS holds the memory area itself in the memory management facility inside the applicable process. Consequently, a process that becomes large in terms of using a large memory area even once never shrinks and continues to have an adverse impact on the system, especially in the case of resident processes. The facility for monitoring the memory size of server processes can prevent memory shortages because it terminates even resident processes.
Application criterion
Apply this facility when the amount of memory space used by a HiRDB server process becomes large, resulting in memory shortages.
Specification guidelines
  • Maximum value for this operand
    Normally specify a value by considering the maximum processing capability of HiRDB. Assuming the maximum number of SQL statements that can execute concurrently, which is dependent on the maximum number of concurrent connections, determine for this operand a value that satisfies the following condition in each unit:
    a[Figure] (b + c) < d
    a: Number of server processes in the unit (maximum number of concurrent connections[Figure] number of servers in the unit)
    b: Virtual memory size for one server process immediately following HiRDB startup
    c: pd_svr_castoff_size operand value
    d: Memory size that can be allocated to a unit (memory size excluding the area used by other programs)
  • Minimum value for this operand
    If the value specified for this operand is smaller than the memory size needed for normal SQL processing, the efficiency of making processes resident will deteriorate, resulting in frequent process terminations and restarts. Each time this occurs, a message is output to the syslogfile or the message log file, resulting in further performance degradation. To prevent this, select for this operand a value that satisfies the following condition for each server:
    a - b < c
    a: Server process virtual memory size following SQL process termination or utility shutdown
    b: Virtual memory size for server process immediately following HiRDB startup
    c: pd_svr_castoff_size operand value
The virtual memory size can be determined by an OS command (for example, the top command in HP-UX).
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
When 0 is specified for this operand, the facility for monitoring the memory size of server processes is not applied.
5) 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 configuration, this operand specifies 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.
Advantage
The asynchronous READ facility is especially effective (improves performance) when character special files, for which input and output take a long time, are used. Conversely, when regular files or Hitachi disk array system disks are used, for which input and output do not take a long time, the asynchronous READ facility might not have much effect for the following reasons:
  • Input/out time does not overlap with CPU time most of the time.
  • Communication processing has a large overhead.
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 configuration) 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[Figure] 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 (number of asynchronous READ processes), see the HiRDB Version 9 System Operation Guide.
Operand defaults
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.
Relationship to other operands
If you change the value of this operand, re-evaluate the value of the pd_max_server_process operand.
Operand rule
If you specify 0 for this operand, the asynchronous READ facility is not used.
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 a HiRDB parallel server configuration
  • Formula for size of shared memory used by global buffers under Estimating the memory size required for a HiRDB parallel server configuration
  • Calculation of required memory under Estimating the memory size required for a HiRDB parallel server configuration
  • Estimating HP-UX OS parameter values
  • Formula 2 under Formulas for the size of the shared memory used by a dictionary server
  • HiRDB parallel server configuration under Determining Environment Variables Related to the Number of Resources
6) pd_dfw_awt_process = number-of-parallel-writes-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 a HiRDB parallel server configuration
  • Calculation of required memory under Estimating the memory size required for a HiRDB parallel server configuration
  • Formula 4 under Formulas for the size of the shared memory used by a dictionary server
  • HiRDB parallel server configuration under Determining Environment Variables Related to the Number of Resources