# Varification in external DB **URL:** \ **Category:** CDB and CDB API\ **Created:** [August 3, 2016, 12:22pm UTC](https://dmap-community.ductus.global/t/varification-in-external-db/611 "2016-08-03T12:22:39Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![InbalAmram](https://avatars.discourse-cdn.com/v4/letter/i/0ea827/32.png) [@InbalAmram](https://dmap-community.ductus.global/u/InbalAmram)\ **Post date:** [August 3, 2016, 12:22pm UTC](https://dmap-community.ductus.global/t/varification-in-external-db/611/1 "2016-08-03T12:22:39Z")
Hi, we are working with external DB. All set commands are implemented with return CONFD\_ACCUMULATE. we implemented the transaction callbacks as discribed in chapter 7 of the user guide. the commit in our DB is done one the prepare call back with all set commands that were accumulated. we would like to have an application varification code. As I understand, the right place to do it is in the validate state. 1. can I use the trans\_lock call back for that? Is the syntax validation was done in that point? Arevthe accumulate commands being sent as part of the trans\_lock callback? 2. Can you recommand on other callback to implement? Regards and thanks Inbal ---
**Author:** ![waitai](https://yyz2.discourse-cdn.com/flex010/user_avatar/dmap-community.ductus.global/waitai/32/436_2.png) [@waitai](https://dmap-community.ductus.global/u/waitai)\ **Post date:** [August 3, 2016, 10:35pm UTC](https://dmap-community.ductus.global/t/varification-in-external-db/611/2 "2016-08-03T22:35:39Z")
I assume by verification, you meant validation. To perform your own validation for constraints that can’t be expressed in your data models, you will need to specify validation points in your data model as described in Chapter 9.6 on Validation Points and implement the corresponding C code to perform the validating logic as described in Chapter 9.7 on Validating Data in C. Your validation callpoint will either be invoked manually with the validate command or at the validate phase of a transaction.