In order to use Pervasive Encryption on a CA IDMS database or journal file, VSAM must be used as the access method.
This is described at Using Pervasive Encryption with CA IDMS.
The documentation for defining IDMS journals as VSAM files contains errors when describing the relationship between the IDMS journal buffer page size and the VSAM file CI size.
In DISK JOURNAL Statements (scroll to "Block size of Disk Journal File" ), it says they should be the same.
In Journal Buffers and Journal Sizes (scroll to "Sizing Journal Buffers"), it says the IDMS journal buffer page size should be 8 more than the CI size.
It is correctly documented in JOURNAL BUFFER Statements.
The IDMS journal buffer page size should be 8 bytes less than the VSAM CI size.
Note also that when defining the VSAM file, the CI size actually used may be more than the value specified as input.
Re-display the file with LISTCAT in order to confirm the size used.
Failing to abide by this requirement may result in the DB002255 error when attempting to FORMAT the journal file.