Always check the default system log when an error is first encountered.

Audit log only occurs on the default domain.

Captured IP packets are stored in pcap format. Need a tool to explore the data such as ethereal. The packet capture file is in the temporary directory.

Probes and debug level logging will create a noticeable slowdown.

Error reports are stored in temporary.

Log levels: debug captures the most information. emergency captures the least.

XML Capture: Captures every XML message that comes to the box.

Event sources: Generate events. Similar to a pub/sub.

Log Targets: Subscribe to the Event Sources.

Log Targets do not capture actual messages. Log action in a processing rule will do that.

Levels Emergency, Alert and Critical are rare.

Error Handling:

An Error-Rule will automatically run if the match is successful.

On-Error will overrule the Error-Rule  but can call an Error-Rule.

In the scenario of On-Error1 -> TransForm -> On-Error2 and the transformation fails, the On-Error1 will fire. On-Error is applicable to all actions AFTER it. If another on-error is included, then it will ‘protect’ the actions after it instead.

On-Errors can be used to capture the actual error that caused the problem. An error-rule will return a very generic message.

var://service/error-message  , var://service/error-code, var://service/error-subcode , var://service/transaction-id

<xsl:message ..> can be used to generate a log entry in an XSLT.

cURL -v can output more information for client-side errors but you are likely looking at the wrong side of your issue.