Segment size (blob)

Segment sizes are specified for blob fields. This can be done using the Domain Editor or the Table Editor (started from the IBExpert DB Explorer).

A blob segment size can be defined, to increase the performance when inputting and outputting blob data. This should roughly correspond to the data type size. With a memo field, for example, for brief descriptions which could however, in individual cases, be considerably longer, the segment length could be defined as 100 bytes, whereby the blob data type is processed in 100 byte blocks.

When processing videos or large graphics in the database, a large segment length should be selected. The maximum length is 65536 bytes. This is because all blob contents are stored in blocks, and are fetched via these blocks. A typical segment size from the old days is 80 (because 80 characters fit onto one monitor line).

When a blob is extracted, the Firebird/InterBase® server reads the number of segments that the client has requested. As the server always selects complete blocks from the database, this value can in effect be ignored on modern powerful computers. 2048 is recommended as a standard since version InterBase® 6.