necessary new and modified containers are transferred between the calling applications, to optimize the performance of the calling mechanism. Providing that containers separate different parameter structures, the calling applications benefit from complete access to the data content in all containers that are in scope. 1.11 Threadsafe Web commands All the EXEC CICS Web API commands have been made threadsafe. These are WEB READ, WEB WRITE, WEB SEND, WEB RECEIVE, WEB RETRIEVE, WEB STARTBROWSE, WEB READNEXT, WEB ENDBROWSE, WEB EXTRACT, EXTRACT WEB, EXTRACT TCPIP, and EXTRACT CERTIFICATE. This removes the requirement for CICS to return to the quasi-reentrant task control block (QR TCB) to execute these commands, so applications (both JavaTM and non-Java) that use these commands should be able to obtain the performance improvements resulting from reduced TCB switching. Also threadsafe are the new Web API commands in support of outbound HTTP: WEB OPEN, WEB CLOSE, WEB CONVERSE, and WEB PARSE URL. 1.12 64-bit addressing toleration