Thread concepts

A DRA thread is a DRA structure that connects a CCTL task or a z/OS® application program task with an IMS DB task that can process those calls. A single DRA thread is associated with every CCTL or ODBA thread. CCTL threads cannot establish a connection with more than one DRA thread at a time.

A DRA thread is a DRA structure that connects:

• A CCTL task (which makes database calls to IMS DB) with an IMS DB task that can process those calls. A CCTL thread is a CCTL task that issues IMS DB requests using the DRA.
• A z/OS application program task (which makes database calls to IMS DB) with an IMS DB task that can process those calls. An ODBA thread is a z/OS task that issues IMS DB calls using the DRA.

A single DRA thread is associated with every CCTL or ODBA thread. CCTL threads cannot establish a connection with more than one DRA thread at a time.

When the DRA Open Thread option is used, threads sign on to IMS when they are scheduled for a request. This behavior causes the IMS commands /DISPLAY CCTL, /DISPLAY ACTIVE REGION and /DISPLAY ACTIVE THREAD to show different values for the MINTHRD output field compared to a non-Open Thread system configuration. Because thread TCBs are not attached, MINTHRD does not apply to the number of threads attached at DRA initialization. However, it does indicate how many thread structures IMS allocates during initialization. After IMS begins scheduling PSBs, those threads appear in the command output as normal.