In this contex, "SDR" appears in adjective context for "database", so the choice between the/a is strictly in classic context of "the database" or "a database" (depending on a broader context), and the acronym doesn't change a thing (except choice between a/an if that's what you pick; in this case the first letter of acronym is a vowel in pronunciation so an es-... ).
The situation would be different, if you abbreviated System for Definitions' Retrieval Database to SDRD - in that case you'd get to choose freely between Integration of SDRD and Integration of the/an SDRD (choice between the and an according to classic rules, if you integrate one random SDRD out of many, then an, if you pick a specific one, the)