The invention relates to the sequencing of a target polynucleotide sequence, immobilized on a solid support, using the polymerase reaction to extend a suitable primer and characterizing the sequential addition of labelled bases. The CPU is provided with a CKD record access library and a VSAM access library which accesses in a FBA format the VSAM record stored by the other CPU in a CKD format in the disk subsystem and allows the access by an application program of the CPU as a VSAM record based on VSAM control information. These handles effectuate a more effective and efficient operation of the immersion blender. The new storage level order applied in the VMs.