Commit log (CLOG)
commit log (
CLOG) maintains the states of all transactions, and is part of the concurrency control mechanism. The commit log is allocated to shared memory and used throughout transaction processing. Files associated with the commit log are located in the data directory in the
pg_clog subdirectory. Specifically, pg_clog contains records of the commit status for each transaction that has been assigned an
Until PostgreSQL 7.1, transaction logs were maintained in a system catalogue table (pg_log, not to be confused with the former data directory subdirectory pg_log). See 2589735d for details of the change.