Note the following points when setting up your test and/or production systems.
You will need to determine the number of DBCTLs you require in a single-MVS environment; for example, one DBCTL subsystem for the whole MVS™ image, or one DBCTL subsystem for each CICS® system in single-MVS environment. Balance the number of DBCTLs within a single MVS image against the amount of CSA needed. Also, be aware of the need to differentiate DBCTL systems on the same MVS image to avoid causing any confusion between subsystems.
You are recommended to have only one production DBCTL in a single-MVS environment. Normally, this should be large enough to serve all CICS Transaction Server for z/OS®, Version 3 Release 1 systems within one MVS image. For multiple CICS systems with local and remote DL/I, running in several MVS images using IMS™ data sharing, count the number of DL/I threads needed. If the sum of these threads, plus the number of expected active BMPs is less than 255, you should need only one DBCTL without data sharing.
You need one log for each DBCTL, so bear in mind that logging can become more complex the more DBCTLs you have. Balance the need for multiple DBCTLs against the logging procedures you will need. However, log throughput time should be improved compared with local DL/I, because DBCTL uses the write ahead data set (WADS), which can reduce the elapsed time needed for a log write.