Some prior activity accessed any of the Datacom the Dynamic System Tables (DBID 1000) causing it to be opened so it would need to be CLOSEd.
Add "COMM DBID=100,OPTION=CLOSE" after the SET and before the COMM OPTION=CONSOLE in STEP1 of BDACTDYN as shown below and rerun BDACTDYN:
//STEP1 EXEC PGM=DBUTLTY,REGION=0M
// INCLUDE MEMBER=B15STLIB
// INCLUDE MEMBER=B15DDCXX
// INCLUDE MEMBER=B15DDOUT
//SYSIN DD *