The XDEPDYN control option is used to control the dynamic updating of the Cross-dependency data set. If XDEPDYN is set to Y, then the Cross-dependency data set is kept in sync with changes to the accounting data set. XDEPDYN may be set to N if the extra I/O activity is causing performance problems. The XDEPUPDT service should then be used to synchronise the Cross-dependency data set with the accounting data set.