In the following descriptions, large volumes and large files will be referred to as “large objects”.
The continual growth of disk storage capacity and of data that needs to be available online has been taken into account in BS2000 in the enlargement of previously available disk and file sizes of around 32 GB. The following maximum values apply:
Capacity of a pubset or volume set: approx. 4 TB (2.147.483.647 PAM pages)
Capacity of a volume: approx. 2 TB (1.073.741.824 PAM pages)
File size: approx. 4 TB
This means that within the operating system, 4-byte block numbers and 4-byte counters must be used systematically for file sizes and disk sizes.
Block numbers and block counters become visible at different interfaces to the user in BS2000. Although 4-byte fields have been used exclusively in all new versions of these interfaces, some old interface versions may still use 3-byte fields. This may lead to compatibility problems for files >= 32 GB (and in some rare cases also for volumes >= 32 GB).
The compatibility aspect has been taken into account in that new pubset types have been created as special containers for large objects. This has allowed the previous world of “small objects” to be separated off and facilitates the successive introduction of large volumes and large files.
Different conditions apply, however, when introducing large volumes and large files.
The introduction of large volumes is designed to allow simple, low-cost expansion of capacity in the Data Center. This process is not visible to users or programs.
Large files are necessary in order to facilitate further growth of applications, where the size of individual (and generally relatively few) files will exceed the former limit of 32 GB in the near future.
In this context, it will be necessary in some cases to modify the programs affected, that, for instance, use old versions of particular interfaces or implicitly assume a maximum file size of 32 GB, in order to guarantee data integrity when the 32-GB limit is exceeded. Programs that are not designed to work with large files are not affected.