Chapter 3: Monitor Client Library Functions

Callback function

Description

Callback functions are user-defined functions that notify an application when an event has occurred. These functions are registered with Monitor Client Library API calls for:

Alarms
Error information

When either of the above events occur, a callback function is executed.

Syntax

SMC_VOID CallbackFunction
 (SMC_CONNECT_ID clientId,
 SMC_COMMAND_ID commandId,
 SMC_VOIDP userDataHandle)

Parameters

clientId: identifies the connection.

commandId: identifies the instance of a command.

userDataHandle: user data pointer for a given connection. An application can set this pointer by using smc_connect_props.

Usage

Accessing callback data

When an event triggers a callback function, you can request information about the event. Data is accessed by calling smc_get_command_info from within the callback function. This function takes a connection ID, a command ID, and an enumerator constant that identifies which piece of data the user is interested in. The data available depends on the type of callback. Table 3-3 describes the data available for alarm callbacks. Table 3-4 describes the data available for error callbacks.

**Table 3-3: Data available for alarm callbacks**
Information type	Description
SMC_INFO_ALARM_ACTION_DATA	String supplied for alarmActionData upon creation of the alarm.
SMC_INFO_ALARM_ALARMID	Identifies the alarm.
SMC_INFO_ALARM_CURRENT_VALUE	Current value that met or exceeded the alarm threshold.
SMC_INFO_ALARM_DATAITEM	Data item on which the alarm was set. Points to a SMC_DATAITEM_STRUCT.
SMC_INFO_ALARM_ROW	Row containing the data item value that triggered the alarm.
SMC_INFO_ALARM_THRESHOLD_VALUE	Threshold value defined for this alarm.
SMC_INFO_ALARM_TIMESTAMP	Time (in the Adaptive Server time zone) marking the end of the sample interval in whose data the alarm condition was met.
SMC_INFO_ALARM_VIEWID	Identifies a view created on the connection.

**Table 3-4: Data available for error callbacks**
Information type	Description
SMC_INFO_ERR_MAPSEVERITY	Monitor Client Library severity level.
SMC_INFO_ERR_MSG	Text of the error message. (See Appendix D, “Troubleshooting Information and Error Messages”.)
SMC_INFO_ERR_NUM	Number of the error.
SMC_INFO_ERR_SEVERITY	Severity of the error message.
SMC_INFO_ERR_SOURCE	Source of the error message. One of the following: SMC_SRC_UNKNOWN – not known SMC_SRC_HS – Historical Server SMC_SRC_SMC – Monitor Client Library SMC_SRC_CT – Client Library SMC_SRC_SS – Adaptive Server SMC_SRC_SMS – Monitor Server
SMC_INFO_ERR_STATE	State of the error. Useful for technical support in diagnosing internal errors.

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