Using version 1.5 aggregates and extended (v5) directories

CAUTION:

Do not use zFS version 1.5 aggregates until you have finished migrating all of your systems to z/OS V2R1 or later. Version 1.5 aggregates are not supported on releases prior to z/OS V2R1. All systems in a sypslex must be a V2R1 level or later before any version 1.5 aggregates on any system in the sysplex are implemented. End of change

Beginning in z/OS® V2R1, zFS supports a new version aggregate, the version 1.5 aggregate. The current aggregates are version 1.4 aggregates. Version 1.5 aggregates support extended (v5) directories. Extended (v5) directories provide the following benefits:

They can support larger directories with performance.
They store names more efficiently than v4 directories.
When names are removed from extended (v5) directories, the space is reclaimed, when possible, unlike v4 directories where space is not reclaimed until the directory is removed.

Version 1.5 aggregates have a larger architected maximum size than version 1.4 aggregates (approximately 16 TB versus approximately 4 TB). Also, extended (v5) directories can support more subdirectories than v4 directories (4G-1 versus 64K-1).

Start of change Because version 1.5 aggregates will benefit all environments that consist of systems that are all at release z/OS V2R1 or later, you are encouraged to use this function after all or your systems have been migrated to z/OS V2R1 or later. End of change Version 1.5 aggregates can contain both extended (v5) directories and v4 directories and either can be a subdirectory of the other, while version 1.4 aggregates cannot contain extended (v5) directories. Version 1.5 aggregates can be mounted on directories that are contained in version 1.4 aggregates, and the reverse is also allowed.