Sometime you tried to insert some record in the table, if the system shows Cannot create a record in Table () , The record already exists. Generally we know that, this issues is caused due to Duplicate value. But here is the trick, so even i have checked the Index values which is allow duplicate yes. But still why this issue.. Basically we know that dynamics AX has invisible Index in every Table which is Recid, so this Recid is generating from SystemSequences Table( field nextval). So this SystemSequences table contains every table Id and its next recid value in nextval field, so if it has a value with an already issued record id, you can increase the number. To access this SystemSequences table you have to use SQL Management studio, Better it’s recommended to stay away from this table.
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