Firebird 2.1 Release Notes

Global Improvements in Firebird 2.1
Configuration and Tuning
Increased Lock Manager Limits & Defaults
D. Yemanov
Feature requests CORE-958 and CORE-937
• the maximum number of hash slots is raised from 2048 to 65,536. Because the actual setting should be
a prime number, the exact supported maximum is 65,521 (the biggest prime number below 65,536). The
minimum is 101.
• the new default number of hash slots is 1009
• the default lock table size has been increased to 1 Mb on all platforms
Page sizes of 1K and 2K Deprecated
D. Yemanov
Feature request CORE-969
Page sizes of 1K and 2K are deprecated as inefficient.
Note
The small page restriction applies to new databases only. Old ones can be attached to regardless of their page
size.
Enlarge Disk Allocation Chunks
V. Khorsun
Feature request CORE-1229
Until v.2.1, Firebird had no special rules about allocating disk space for database file pages. Because of dependencies
between pages that it maintains itself, to service its “careful write” strategy, it has just written to newly-allocated
pages in indeterminate order.
For databases using ODS 11.1 and higher, Firebird servers from v.2.1 onward use a different algorithm for
allocating disk space, to address two recognised problems associated with the existing approach:
1. Corruptions resulting from out-of-space conditions on disk
The indeterminate order of writes can give rise to a situation that, at a point where the page cache contains
a large number of dirty pages and Firebird needs to request space for a new page in the process of writing
them out, there is insufficient disk space to fulfil the request. Under such conditions it often happens that the
administrator decides to shut down the database in order to make some more disk space available, causing
the remaining dirty pages in the cache to be lost. This leads to serious corruptions.
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