https://www.ibm.com/docs/en/ims/15.1.0?topic=haldb-allocating-psindex-vsam-ksds-data-sets
IMS 15 - Database administration - Allocating PSINDEX VSAM KSDS data sets
Allocate a VSAM KSDS data set for each partition of the PSINDEX by using the IDCAMS DEFINE statement.
database administrationimsvsamsets
https://www.ibm.com/docs/en/ims/15.3.0?topic=formats-secondary-index-psindex-database-vsam-only
IMS 15.2 - Diagnosis - Secondary index or PSINDEX database (VSAM only)
The LRECL Format on Device and in Buffer Pool are described.
imsdiagnosissecondary
https://www.ibm.com/docs/en/ims/15.1.0?topic=types-partitions-in-phdam-phidam-psindex-databases
IMS 15 - Database administration - Partitions in PHDAM, PHIDAM, and PSINDEX databases
You can view a HALDB database, whether it is a PHDAM, PHIDAM, or a PSINDEX database, as a single database whose records are divided into manageable sections...
database administrationimspartitions