What is the default value for collocation defining a primary sequential storage pool?

This means that, by default, files from different clients are grouped together in storage pool volumes to optimize space utilization. This information is available in the IBM Spectrum Protect for AIX [1]: Administrator's Reference, which is one of the official documentation resources for this product.

https://www.ibm.com/docs/en/spectrum-protect/8.1.14?topic=storage-optimizing-operations-by-enabling-collocation-client-files