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Managing DB2 Recovery Data Sets with SMS 67
7.2 BSDS
The bootstrap data set (BSDS) contains the information required by DB2 to start
the subsystem in normal circumstances. It also handles the restart and recovery
in any abnormal circumstance. For example, all log data sets (active and archive)
are automatically registered within the BSDS.
Data Organization
The BSDS is a VSAM KSDS. The data control interval is 4 KB; the index control
interval is 1 KB. Figure 19 on page 67 shows an example VSAM definition of a
BSDS.
Performance
While DB2 is executing, the BSDS is updated periodically. The frequency of these
updates is not high, but is dependent on general DB2 subsystem activity. For
example, the BSDS is updated at every DB2 checkpoint and at every archive
process.
Availability
The BSDS is a critical resource for DB2. Because of this, DB2 has implemented
dual copies for the BSDS. DB2 requires the presence of two copies of the BSDS
during restart, to ensure high availability. While DB2 is running, a BSDS may fail
and DB2 continues operating with one BSDS. The second BSDS should be
restored as soon as possible, to avoid DB2 shutdown, which would occur if the
last available BSDS also fails.
Figure 19. Example VSAM Definition of one BSDS
7.2.1 Storage Class
BSDSs use a Storage Class with guaranteed space. This allows the DB2
administrator to decide the location of each BSDS.
• SCDBACTL
7.2.2 Management Class
No SMS management is required for the BSDS data sets. The following
Management Class has been defined for this purpose.
• MCDBACTL
DEFINE CLUSTER -
( NAME(DB2V610Z.BSDS01) -
VOLUMES(SBOX10) -
REUSE -
SHAREOPTIONS(2 3) ) -
DATA -
( NAME(DB2V610Z.BSDS01.DATA) -
RECORDS(180 20) -
RECORDSIZE(4089 4089) -
CONTROLINTERVALSIZE(4096) -
FREESPACE(0 20) -
KEYS(4 0) ) -
INDEX -
( NAME(DB2V610Z.BSDS01.INDEX) -
RECORDS(5 5) -
CONTROLINTERVALSIZE(1024) )