RDB$FORMATS stores information about changes in tables. Each
time any metadata change to a table is committed, it gets a new format number.
When the format number of any table reaches 255, the entire database becomes
inoperable. To return to normal, the database must be backed up with the
gbak utility and restored from that backup copy.
||Table or view identifier
||Table format identifier—maximum 255. The critical time
comes when this number approaches 255 for any table or
||Stores column names and data attributes as BLOB, as they were
at the time the format record was created