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arangodb/Documentation/DbaManual/DatafileDebugger.md

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Datafile Debugger

@NAVIGATE_DbaManualDatafileDebugger @EMBEDTOC{DbaManualDatafileDebuggerTOC}

In Case Of Disaster

AranagoDB uses append-only journals. Data corruption should only occur when the database server is killed. In this case, the corruption should only occur in the last object(s) that have being written to the journal.

If a corruption occurs within a normal datafile, then this can only happen if a hardware fault occurred.

If a journal or datafile is corrupt, shut down the database server and start the program

unix> arango-dfdb

in order to check the consistency of the datafiles and journals. This brings up

___      _         __ _ _           ___  ___    ___ 
   /   \__ _| |_ __ _ / _(_) | ___     /   \/ __\  / _ \
  / /\ / _` | __/ _` | |_| | |/ _ \   / /\ /__\// / /_\/
 / /_// (_| | || (_| |  _| | |  __/  / /_// \/  \/ /_\\ 
/___,' \__,_|\__\__,_|_| |_|_|\___| /___,'\_____/\____/ 

Available collections:
  0: _structures
  1: _users
  2: _routing
  3: _modules
  4: _graphs
  5: products
  6: prices
  *: all

Collection to check:

You can now select, which collection you want to check. After you selected one or all collections, a consistency check is performed.

Checking collection #1: _users

Database
  path: /usr/local/var/lib/arangodb

Collection
  name: _users
  identifier: 82343

Datafiles
  # of journals: 1
  # of compactors: 1
  # of datafiles: 0

Datafile
  path: /usr/local/var/lib/arangodb/collection-82343/journal-1065383.db
  type: journal
  current size: 33554432
  maximal size: 33554432
  total used: 256
  # of entries: 3
  status: OK

If there is a problem with one of the datafile, then the database debugger tries to fixed that problem.

WARNING: The journal was not closed properly, the last entries is corrupted.
         This might happen ArangoDB was killed and the last entries were not
         fully written to disk.

Wipe the last entries (Y/N)?

If you answer Y, the corrupted entry will be removed.

If you see a corruption in a datafile (and not a journal), then something is terrible wrong. These files are immutable and never changed by ArangoDB. A corruption in such a file is an indication of a hard-disk failure.