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The dbfsck utility allows checking of the volume integrity (in case
problems are suspected) or to attempt to get a corrupted volume
fixed sufficiently so a sequential dbexport could be performed
to recover the data. It is not a magic repair tool.
Using dbfsck for data recovery should be considered the last
option.
The dbfsck utility is an "offline utility" that directly accesses the
database server volume files and may only be used when the database
server is not active. The dbfsck read-only mode may be used if the
database server is in on-line backup mode.
Note: dbfsck should not be run on a database which was
not shutdown cleanly. Transactions from the log volume have not been
applied and dbfsck could report wrong positives.
usage: dbfsck [options]
options:
-d flags - debug flags
-c cfg - configuration file name
-b size - Buffer cache size (MB)
-v - output volume overview and informational messages,
output progress info every minute on stdout
write options:
-w - Enable write mode
-a - Automatically fix minor inconsistencies
-y - Answer yes to all questions
Please Note: Enabling write mode and answering 'yes' to non-trivial
questions may cause data loss and could even result in additional
data corruption.
Unless you know what you're doing, you should consider to recover
the database from a backup.
dbfsck by default operates in read-only mode to analyze the
volume consistency. Depending on the amount of data this can take
a considerable time. Any messages (except for -v progress messages)
are output to stderr.
The options are:
- -help
- The -help option displays a brief help text.
- -c eloqdb.cfg
- The -c option specifies the eloqdb configuration file.
The eloqdb configuration file is used to locate the database
volume files. If not specified the default eloqdb.cfg is used.
- -v
- If the -v option is present progress messages are output
(to stdout).
- -w
- The -w option enables dbfsck write mode which allows to repair
inconsistencies. By default dbfsck operates in read-only mode to
analyze volume consistency. In write mode, any repair operation
must be confirmed by the operator unless the option -a or -y is used.
- -a
- The -a option enables dbfsck in write mode to perform safe
repairs automatically without prompting the user.
- -y
- The -y option enables dbfsck in write mode to perform any recovery
operations without prompting.
- -d flags
- The -d option specifies debug flags and is normally not used.
- -b size
- The -b option may be used to specify the size of internal buffer
cache (in MB). The default buffer cache used by dbfsck is 5 MB.
dbfsck should not be used if the database was not shutdown cleanly.
In this case uncommitted transactions may be in the transaction log
which are not applied to the data volume(s). Please run dblogreset
to apply the transaction journal or start the eloqdb to apply the
transaction journal.
Running dbfsck on a "unclean" volume could result in false positives
(incomplete transactions that are in the transaction journal)
or even damage data in write mode.
Consequently, if dbfsck detects that the volumes have not been
shutdown cleanly it will print a warning message and refuse to
run in write mode.
dbfsck uses two passes, each verifying different aspects of the
volume file:
-
PASS 1 - verifying block allocation integrity
Iterates each node's meta information and makes global sanity checks
-
is the NodeBlockList consistent?
-
does every page referred by the NodeBlockList belong to this node?
(node cross-link detection)
-
is every used page really marked "in use" in the volume?
-
PASS 2 - verifying node integrity
Iterates each node's contents and checks its contents in detail,
depending on the particular node type (FixRec, Btree, Pool).
dbfsck uses the following terminology:
- Node : data container, similar to a file
- NodeBlockList : contains references to all used pages in a node
- NodeBlockListContent : synonym for "data page" (a page the block
list refers to)
- FixRec : fixed size records, used for data storage
-> corruptions can be recovered by dbfsck, but usually data is lost
- FixRec free-list : free record bookkeeping information
-> can be safely recovered by dbfsck without data loss
- FixRec meta information : contains data set properties
-> information such as number of used records can be safely recovered
by dbfsck without data loss
- Btree : used for storing index information
-> inconsistencies can typically not be fixed by dbfsck but requires
a database reload (or re-creating the indexes)
- Pool : used for Catalog information
- PoolFreeList : List of free blocks in a pool
-> inconsistencies can normally not be fixed by dbfsck
Note that the dbfsck utility allows to specify node IDs (node numbers) on
the command line. If present, pass 2 does only process the specified nodes.
For HP-UX and Windows, the dbfsck64 utility provides a 64 bit version of dbfsck.
Large database environment sizes (approximately above 400 GB) may require the 64 bit
dbfsck version to overcome a 32 bit address space limitation. If the 32 bit dbfsck
issues a memory allocation failure, the 64 bit dbfsck should be used.
When running dbfsck in write mode:
- Please make sure to have a backup before running dbfsck in
write mode.
- Running dbfsck in write mode will break transactional
consistency and as a consequence, any replicated slave servers need to be
re-synchronized. Also, forward recovery cannot be used to recover
the database unless a new backup is made.
$ dbfsck 2>&1|tee /tmp/dbfsck.log
ELOQUENCE DBFSCK (C) Copyright 2013 Marxmeier Software AG (B.08.20)
Running in On-Line Read-Only mode
PASS 1 - verifying block allocation integrity
PASS 2 - verifying node integrity
done.
The following example uses -v progress messages, redirecting check results to a file.
$ dbfsck -v 2>/tmp/dbfsck.log
ID Type Path
1 DATA /data/db/db01.vol
2 LOG /data/db/db02.vol
3 DATA /data/db/db03.vol
4 DATA /data/db/db04.vol
5 DATA /data/db/db05.vol
6 DATA /data/db/db06.vol
7 DATA /data/db/db07.vol
ID Type Cur.Sz Ext.Sz Max.Sz Free Used
1 DATA 1024.0 1.0 1024.0 0.0 1024.0
2 LOG 63.5 1.0 0.0 63.4 0.1
3 DATA 1024.0 1.0 1024.0 0.0 1024.0
4 DATA 1024.0 1.0 1024.0 0.0 1024.0
5 DATA 1024.0 1.0 1024.0 0.0 1024.0
6 DATA 1024.0 1.0 1024.0 32.1 991.9
7 DATA 152.5 1.0 1024.0 148.9 3.6
Processed 0 of 649749 pages (0%)
Processed 116787 of 649749 pages (17%)
Processed 266858 of 649749 pages (41%)
Processed 369120 of 649749 pages (56%)
Processed 401120 of 649749 pages (61%)
Processed 433120 of 649749 pages (66%)
Processed 462120 of 649749 pages (71%)
Processed 493120 of 649749 pages (75%)
Processed 522120 of 649749 pages (80%)
Processed 552120 of 649749 pages (84%)
Processed 649749 of 649749 pages (100%)
$ cat /tmp/dbfsck.log
ELOQUENCE DBFSCK (C) Copyright 2013 Marxmeier Software AG (B.08.20)
Running in On-Line Read-Only mode
PASS 1 - verifying block allocation integrity
PASS 2 - verifying node integrity
done.
dbcfix utility
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