6.24.1 Points to consider when specifying the number of connections for a group

(1) Points to consider when specifying the maximum number of concurrent connections and the guaranteed minimum number of concurrent connections for a group

Consider the following when you use the client-group facility and you specify a maximum number of concurrent connections and a guaranteed minimum number of concurrent connections for a group:

• What would be the maximum number of concurrent connections to the HADB server?

  Evaluate the value of the adb_sys_max_users operand in the server definition. For details about the adb_sys_max_users operand in the server definition, see the description of the adb_sys_max_users operand in 7.2.1 Operands related to system configuration (set format).

• What would be the maximum number of concurrent connections and the guaranteed minimum number of concurrent connections for a group?

  You can use the adbcltgrp operand in the server definition to specify the maximum number of concurrent connections and the guaranteed minimum number of concurrent connections for a group. For details about the adbcltgrp operand in the server definition, see 7.2.12 Operands and options related to the client-group facility (command format).

• How many connections would be needed for HADB clients and commands that belong to no group?

  The number of connections usable by HADB clients and commands that belong to no group is determined by the maximum number of concurrent connections to the HADB server and by the maximum number of concurrent connections and the guaranteed minimum number of concurrent connections for each group.

  The number of connections usable by HADB clients and commands that belong to no group is within the range of the freely usable number of concurrent connections. The number of freely usable concurrent connections is the maximum number of concurrent connections to the HADB server minus the guaranteed minimum number of concurrent connections for each group.

  Taking this relationship into account, specify the appropriate maximum number of concurrent connections and guaranteed minimum number of concurrent connections for each group.

The following figure provides an overview of the numbers of connections that are allocated when the client-group facility is used.

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(2) How to determine the numbers of connections when the client-group facility is used

This subsection explains how to determine the numbers of connections when the client-group facility is used.

■ How to determine the maximum number of concurrent connections and the guaranteed minimum number of concurrent connections for a group

The maximum number of concurrent connections and the guaranteed minimum number of concurrent connections for a group are determined by the values of the adbcltgrp and adb_sys_max_users operands in the server definition. The HADB clients and commands that belong to a group can use connections within the range of the maximum number of concurrent connections and the guaranteed minimum number of concurrent connections specified for the group. The following table explains the maximum number of concurrent connections and the guaranteed minimum number of concurrent connections for a group.

Table 6‒29: Maximum number of concurrent connections and the guaranteed minimum number of concurrent connections for a group

No.	Type of connection count	Value
1	Maximum number of concurrent connections	The value is determined by the following formula:
2	Guaranteed minimum number of concurrent connections	The value is as follows: Value of the -u option in the adbcltgrp operand in the server definition for the target group

■ How to determine the number of freely usable concurrent connections

The freely usable concurrent connections are available to all HADB clients and commands regardless of whether they belong to a group. Use the following formula to determine the number of freely usable concurrent connections.

Formula

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(3) Relationships among connection counts when the client-group facility is used

The following figure shows the relationships among the different types of connection counts explained in (2) How to determine the numbers of connections when the client-group facility is used when the client-group facility is used.

Explanation:

• The guaranteed minimum number of concurrent connections for the client group (10) and the guaranteed minimum number of concurrent connections for the command group (5) are allocated from the maximum number of concurrent connections to the HADB server (60). Therefore, the remaining connections (45) belong to the freely usable concurrent connections. The freely usable concurrent connections are available to all HADB clients and commands regardless of whether they belong to a group.

• Of the freely usable concurrent connections (45), each group can use up to its maximum number of concurrent connections minus its guaranteed minimum number of concurrent connections. In this example, the client group can use up to its local group's maximum number of concurrent connections (30) minus its guaranteed minimum number of concurrent connections (10) as freely usable concurrent connections (20). The command group can use up to its maximum number of concurrent connections (20) minus its guaranteed minimum number of concurrent connections (5) as freely usable concurrent connections (15).

Note

Depending on the sum of all groups' maximum numbers of concurrent connections, a portion of the freely usable concurrent connections might become available only to HADB clients and commands that belong to no group. The following figure shows the relationship between the number of connections that are available only to HADB clients and commands that do not belong to any group, and the sum of the maximum numbers of concurrent connections for all groups. This figure is based on the settings shown in Figure 6‒6: Relationships among connection counts when the client-group facility is used.

Figure 6‒7: Relationship between the number of connections that are available only to HADB clients and commands that belong to no group and the sum of the maximum numbers of concurrent connections for all groups

Explanation:

If the sum of the maximum numbers of concurrent connections specified for all groups is smaller than the maximum number of concurrent connections to the HADB server, some of the connections will never be used by any group. These connections become available only to HADB clients and commands that belong to no group.

In this example, the sum of the maximum numbers of concurrent connections specified for all groups (50) is less than the maximum number of concurrent connections to the HADB server (60). As a result, 10 connections will never be used by any group. These 10 connections become available only to HADB clients and commands that belong to no group.

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(4) Enabling output of warning messages regarding the maximum number of concurrent connections

By specifying the -w option for the adbcltgrp operand in the server definition, you can have HADB output the warning message KFAA40020-W when the number of concurrent connections approaches the maximum number of concurrent connections available to the group. For details about the adbcltgrp operand, see the explanation of the adbcltgrp operand in 7.2.12 Operands and options related to the client-group facility (command format).

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