Use of Event IDs

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Applications running on systems earlier than AIX® 6.1 and 32-bit applications running on AIX® 6.1 use 12-bit (or 3-hex-digit) event IDs (hook IDs), for a maximum of 4096 IDs. Beginning with AIX® 6.1, 64-bit applications and kernel routines can use 16-bit (or 4-hex-digit) event IDs for a maximum of 65 536 IDs. Event IDs that are permanently left in and shipped with code must be permanently assigned.

If a 16-bit ID is less than 0x1000, its least significant digit must be 0 (in the form of 0x0hh0 where h is a hexadecimal digit).

Tip: A 12-bit hook ID in the form of 0xhhh is equivalent to a 16-bit ID in the form of 0xhhh0 where h is a hexadecimal digit.

To allow you to define events in your environments or during development, a range of event IDs exist for temporary use. Event IDs for temporary use ranges from hex 010 through hex 0FF for applications running on systems earlier than AIX® 6.1 and 32-bit applications running on AIX® 6.1 and later releases. For 64-bit applications and kernel routines beginning with AIX® 6.1, event IDs for temporary use ranges from hex 0100 through hex 0FF0. No permanent (shipped) events are assigned in this range. You can freely use this range of IDs in your own environment. If you do use IDs in this range, do not let the code leave your environment.

Permanent events must have event IDs assigned by the current owner of the trace component. To obtain a trace event id, send a note with a subject of help to aixras@austin.ibm.com.

You should conserve event IDs because they are limited. Event IDs can be extended by the data field. The only reason to have a unique ID is that an ID is the level at which collection and report filtering is available in the trace facility. An ID can be collected or not collected by the trace collection process and reported or not reported by the trace report facility. Whole applications can be instrumented using only one event ID. The only restriction is that the granularity on choosing visibility is to choose whether events for that application are visible.

A new event can be formatted by the trace report facility (trcrpt command) if you create a stanza for the event in the trace format file. The trace format file is an editable ASCII file. The syntax for a format stanzas is shown in Syntax for Stanzas in the trace Format File. All permanently assigned event IDs should have an appropriate stanza in the default trace format file shipped with the base operating system.