https://www.ibm.com/docs/en/ims/15.5.0?topic=parameters-maxpst-parameter-procedures
IMS 15.5 - System definition - MAXPST= parameter for procedures
Use the MAXPST= parameter in procedure to specify the maximum number of partition specification tables (PST) control blocks that the user permits the online...
imssystemdefinitionparameterprocedures