A–Z
Glossary
Plain-language definitions of the Unified Logging terms used across the tool and the blog.
- dsc (shared-cache strings)
- Files in /private/var/db/uuidtext/dsc holding the format strings of the dyld shared cache, used by most Apple framework log messages.
- Firehose chunk
- The tracev3 chunk (tag 0x6001) that holds regular Unified Log entries: log, activity, trace, signpost and loss events.
- .logarchive
- A portable macOS bundle holding a copy of the Unified Log store: tracev3 files, uuidtext and dsc strings, and timesync records.
- Mach continuous time
- The macOS clock, counting from boot and including sleep, used for Unified Log timestamps before conversion to UTC.
- Oversize string
- A tracev3 chunk (tag 0x6002) holding Unified Log argument data too large for its entry, sometimes stored in a later file.
- <private> redaction
- Why Unified Log messages show <private>: values marked private are hidden when logged unless a profile enables private data.
- Signpost
- A Unified Log event marking the start, end or a point of an operation, used for performance measurement rather than diagnostics.
- Statedump
- A Unified Log record (tracev3 tag 0x6003) where a process dumps a block of state, such as a plist, a protobuf or an object.
- Subsystem and category
- The reverse-DNS subsystem and the category an os_log message is logged under, such as com.apple.TCC and access.
- timesync
- Records in /private/var/db/diagnostics/timesync that convert Unified Log Mach times into wall-clock UTC for each boot.
- tracev3
- The binary file format macOS uses to store Unified Log entries: a header, catalogs and LZ4-compressed chunksets of log entries.
- Unified Logging
- The single logging system of macOS since 10.12 Sierra, where the kernel, Apple daemons and os_log clients write their messages.
- uuidtext
- Files under /private/var/db/uuidtext that hold the format strings of each binary, needed to render Unified Log messages.