internal Firebird consistency check (wrong record length (183))
What it means
Every record carries the number of the record format (the table’s layout at the time it was written), and unpacks to the length of that format. wrong record length means a record unpacked to a different length: its bytes, its header or one of its fragments is damaged. Like decompression overran buffer, it is damage to individual records, and the statement that reads the record fails every time.
First: make a copy, and work only on the copy
Stop the Firebird server, or at least make sure nothing is connected to the database. Then copy the file, together with any .delta file next to it (an nbackup lock) and the secondary files of a multi-file database. A copy taken while the server writes to the file is inconsistent, and every repair attempt changes the file it runs on. If the disk itself is failing, copy the file to another disk before anything else.
Then: try Firebird’s own tools
These come with every Firebird installation and often get a database back as a whole: indexes, triggers, users and all. On the copy:
gfix -v -full -n copy.fdb # validate, report only
gfix -mend -full -ignore copy.fdb # let gbak skip damaged records
gbak -b -v -ig -g copy.fdb copy.fbk # back up: no checksums, no GC
gbak -c -v copy.fbk restored.fdb # restore into a new database
Add -user SYSDBA -password ... as your server needs. If gbak -b completes, the restored database is the result: check the row counts of the important tables. gfix -mend throws away the records it cannot read, so compare with the original before you rely on the restored copy.
If gbak still fails: get the data out with fbrescue
fbrescue reads the database file directly, without the Firebird engine, and exports every row it can read. It does not stop at the first damaged record or page, and it never writes to the file. Download the single binary for your system from Releases (Windows, Linux, macOS; nothing to install).
fbrescue scan copy.fdb # what is damaged, by table
fbrescue export copy.fdb --out rescued --format sql # schema.sql + INSERTs per table
--format csv and --format jsonl are there too. Rows that could not be read are listed in rescued/_errors.jsonl with the page and the reason, and the exit status is 2 when anything was left out. To load the result into a new database:
isql -ch UTF8 -i rescued/schema.sql new.fdb
isql -ch UTF8 -i rescued/CUSTOMERS.sql new.fdb # and so on for each table
If you would like help, open an issue and attach the output of fbrescue report copy.fdb: it describes the damage without any of your data, and with table and column names replaced by numbers.
For this error fbrescue reads each record with the format it names. A record that is too short for its format is listed in _errors.jsonl with its page and line; the other records of the table are exported. Tables altered many times are fine: each record is read with the layout it was written with.