IMS is completely different from CICS. DLI calls are database calls and have nothing to do with transaction or DC calls. As Akatsukami indicates SPA stands for "Scratch Pad Area". From the manuals, SPA, in IMS/VS conversational processing, is a work area in main storage or on direct access storage used to retain information from the application program for executions of the application program from the same terminal.
Most fast paced high transaction processing installations do not use the SPA. Make sure that your installation allows it. Also remember that SPA and non-SPA MPP programs do not "talk" to each other.
There are some that still use a SPA - they are not high transaction processing installations and they are few. You can pass info in your linkage section if multiple programs are involved in one transaction. You can hide info on your screen - in your message. Remember that there can be many people using the same program in the region. Once you send a message and then get a message, the data contained in your buffer may not be your data.
This link might be of some more interest: http://publib.boulder.ibm.com/infocente ... a_ref.html