TBLBASE, the tableBASE API, determines what type of environment it is being executed in, and if it is not an IMS MPR, it performs exactly the same as it would in batch. Message processing programs (MPPs) to be tested using IBM’s Batch Terminal Simulator (BTS) can be run in the IMS MPRs without having to relink the MPPs.

TBLBASE should be statically link-edited with each MPP wishing to call tableBASE.

Each time an MPP is loaded into an MPR, TBLBASE considers it as a distinct thread of execution and initializes it with a fresh copy of the default LIB-LIST, status switches, and VTSNAME. This means that if an MPP is used for more than one transaction before it is reloaded, it must manage the status switches and library search order, LIB-LIST, between transactions.