Basic Buffer handler

The Basic Buffer handler (BB) provides ESDS, OSAM data sets, and OSAM LDS with look-aside buffering services similar to those services provided by the DL/I buffer handler.

BB might yield better performance than the DL/I buffer handler, because HSSR Engine reduces the path length for database calls and uses direct I/O and look-aside buffering methods. However, BB does not provide the immediate-chained sequential I/O or the anticipatory overlapped chained sequential I/O, which are provided by CAB.

BB is used for ESDS, OSAM data sets, and OSAM LDS if a BUF control statement is specified, in the HSSROPT data set, for the database.

To reduce the path length of an HSSR call, each HSSR PCB and each data set group within each PCB has its own buffers for OSAM, OSAM LDS, and ESDS, which is the same as CAB. If HSSR PCB 1 and HSSR PCB 2 refer to the same database, and look-aside buffering for HSSR PCB 1 is unsuccessful, the buffer handler tries to find the requested data in the BB buffers of HSSR PCB 2. If it finds the data, the buffer of HSSR PCB 2 is copied into a buffer of HSSR PCB 1. Buffers are maintained on a last-referred-to basis.

An output statistical report is provided to the user on the HSSRSTAT data set.