TCB

From CICS Wiki

What is a TCB? (Basic)

A TCB is a control block that represents a task, such as your program, as it runs in an address space. A TCB contains information about the running task, such as the address of any storage areas it has created. Do not confuse the z/OS term TCB with the UNIX data structure called a process control block or PCB. Compared to windows it's like a thread.

TCBs are created in response to an ATTACH or ATTACHX macro. By issuing the ATTACH/ATTACHX macro, a user program or system routine begins the execution of the program specified on the ATTACH/ATTACHX macro, as a subtask of the attacher's task. As a subtask, the specified program can compete for processor time and can use certain resources already allocated to the attacher's task.

The region control task (RCT), which is responsible for preparing an address space for swap-in and swap-out, is the highest priority task in an address space. All tasks within an address space are subtasks of the RCT.

An application usually doesn't care about the TCB because it's done by the operating software or software like CICS or DB2.

Roland 19:28, 20 October 2007 (CDT)