Workload assignment

At the beginning of the first unit of work after a database connection is established, the data server assigns the connection to a workload by evaluating the connection attributes of each workload that is enabled.

The order in which the workloads are evaluated is determined by the EVALUATIONORDER column value of each workload in the SYSCAT.WORKLOADS table. If a workload with matching connection attributes is found, the data server checks whether the current session user has the USAGE privilege on the workload. If the user has the USAGE privilege on the matching workload, the workload assignment is complete, and the connection is assigned to that workload. If the user does not have the USAGE privilege on the matching workload, the data server continues to evaluate workloads until it finds a matching workload on which the session user has the USAGE privilege. If no matching workload is found, the data server attempts to use the SYSDEFAULTUSERWORKLOAD workload. If the current session user does not have the USAGE privilege on that workload, SQL4707N is returned, and the unit of work is rejected. Otherwise, the connection is assigned to the SYSDEFAULTUSERWORKLOAD workload.

You can set the evaluation order by using the POSITION keyword of the CREATE WORKLOAD or ALTER WORKLOAD statement, as follows:

By specifying the absolute position of the workload in the evaluation order, as shown in the following example:
```
CREATE WORKLOAD...POSITION AT 2
```
POSITION AT 2 means that the workload is to be positioned second in the evaluation order. A matching workload that is positioned higher in the evaluation order is evaluated first. That is, if the workloads at both position 2 and position 3 match, the workload at position 2 is evaluated before the workload at position 3.

If the position that you specify on the CREATE WORKLOAD or ALTER WORKLOAD statement is greater than the total number of existing workloads, the workload is positioned next to last in the evaluation order, before the SYSDEFAULTUSERWORKLOAD workload. The effect is the same as specifying POSITION LAST on the CREATE WORKLOAD or ALTER WORKLOAD statement.
By using the POSITION BEFORE workload-name or POSITION AFTER workload-name keyword, where workload-name is an existing workload. This keyword specifies the position of a new or altered workload relative to another workload in the evaluation order, as shown in the following example:
```
ALTER WORKLOAD...POSITION BEFORE workload2
```

If you do not specify the POSITION keyword, by default, the new workload is positioned after the other defined workloads in the evaluation order but before the SYSDEFAULTUSERWORKLOAD workload, which is always considered last.

Workload reassignment

A connection can potentially change its assigned workload at each unit of work boundary if one of its connection attributes or the set of workload definitions changes. A unit of work boundary is the point when a connection disassociates with its current transaction. The following events cause a unit of work boundary: Commit, rollback, XA end (success), XA commit, and XA rollback.

The workload assignment is reevaluated at the beginning of a new unit of work if the data server detects that one of the following events occurred:

A relevant connection attribute changed. See the table in Work identification by origin with workloads for a list of connection attributes that you can specify in a workload definition. Workload reevaluation also occurs if the current session authorization ID changes because the database connection switches because of a trusted context. For more information, see Trusted contexts and trusted connections.
You created or altered a workload.
You granted the USAGE privilege on a workload to a user, a group, or a role or revoked the USAGE privilege on a workload from a user, group, or role.

A connection cannot be reassigned to a different workload while an activity that spans a unit of work boundary is still active. An activity can be an operation that maintains resources across multiple UOWs, such as a load operation, a stored procedure or table function, or a WITH HOLD cursor. The current workload occurrence runs until all activities complete. The workload reassignment then occurs at the beginning of the next unit of work.

An attempted workload assignment or reassignment results in an SQL4707N error if either of the following cases exists:

The data server attempts to assign the connection to a workload that is dispermitted access to the database. For more information, see Preventing occurrences of a workload from accessing the database.
The data server attempts to assign the connection to the SYSDEFAULTUSERWORKLOAD workload, but the current session user does not have the USAGE privilege on this workload.

If you have ACCESSCTRL, DATAACCESS, DBADM, SECADM, or WLMADM authority, you can assign your database connection to the SYSDEFAULTADMWORKLOAD workload, the default administrator workload. See Taking corrective action using the default administration workload for more information.

XA transactions and workload reassignment

XA calls such as XA_END (success), XA commit, and XA rollback issue a Db2 COMMIT or ROLLBACK, which indicates the end of a unit of work. Because workload reevaluation can occur at the beginning of a unit of work, these XA calls can initiate workload reevaluation, although the reason for workload reevaluation is not directly related to the XA transaction itself.