Neo4j in production - Neo4j in Action - page 310

Figure 11.3. Recap of where transaction logs fit into the overall Neo4j architecture
In chapter 7 youlearnedthatNeo4jisafullyACID-compliant(atomic,consistent,isolated,
durable) database. Many ACID-based systems (Neo4j included) use what's known as a
write-aheadlog(WAL)asthemechanismforprovidingtheatomicityanddurabilityaspects
of ACID. The use of a WAL means that whenever a transaction is committed, all changes
are written (and physically flushed) to the active transaction log file on disk before they're
applied to the store files themselves. Recall that the use of the filesystem cache means that
writes tothestorefiles maystill onlybeinmemory—the OSisinchargeofdeciding when
to flush these areas to disk. But even if the system crashes and committed changes haven't
been applied to the physical store files, the store files can be restored using these transac-
tion logs.
All transaction log files can be found in the top level of the Neo4j database directory and
they follow the naming format nioneo_logical.log.*.
Behind the scenes—recovering from an unclean shutdown