Walter,
> As I understand it when a record is deleted a new primary version with a > mark (a flag) is put on it indicating that fact and the previous version of > the record is copied on another location (same page if there is room or > another page if there is not) > > Is that true? > More or less. A new "deleted stub" record - a header with no data - is created and stored on the record's home page. If there's not room on the home page for the deleted stub, then the oldest version of the record on the page will be moved elsewhere. It's probably worth noting, for those who are thinking about implementing relational database managers, that records can be relocated on page freely. The record number (RDB$DB_KEY and all its aliases) is the value used in indexes to identify a specific record. That number consists of a pointer page identifier - the ordinal number of a row in RDB$PAGES for pointer pages for that table - plus the offset on the pointer page that contains the page number of the record's home page, plus the offset of an index on that page that contains the offset and length of the data on page. So... 1) Reorganizing data on a page just requires swapping values in the index for that page to maintain stable record numbers. 2) All versions of a record use the same record number. 3) Updating a record does not require changing all the indexes on the table. If the key doesn't change, neither does the index. However, once a record has been deleted and garbage collected, its record number is released and will be reused, so record numbers are not stable outside of a single transaction - unless you use a switch to make record numbers stable for your connection. Record numbers will change after a gbak restore. Good luck, Ann [Non-text portions of this message have been removed]
