The cross-system object lock (CSOL) ensures that when an object is changed in a managed system, it is locked in the SAP Solution Manager system. A lock conflict will raise and one popup screen with error (termination) or warning message for the second developer will be shown to inform him that the same object is currently locked by another transport request and it is not yet imported to the production system, but as of SolMan 7.2 SP08 you can control your software distribution more flexibly. Update ST-PI to the latest version on all managed systems reporting imports (see BAdI CTS_IMPORT_FEEDBACK and implementation name /SDF/IMPORT_FEEDBACK, implementation class/SDF/CL_IM_IMPORT_FEEDBACK for details)
SAP Security Blog