HP Large Objects System Management Manual

HP Large Objects System Management Manual – 543599.001
example, if more objects are expected of a certain size, then more BuddySpace files
would be configured to house those more frequently used sizes.
3.1.4 Free Space Map (FSM)
The FSM is the key to the usage of the BuddySpace. Therefore, there must be one
FSM per BuddySpace. The FSM is also an unstructured Enscribe file, existing in the
same subvolume as the BuddySpace to which it relates.
3.1.5 Objects
Each object that is stored in the system is externally referenced by the BuddyGroup,
and the objectStoreId assigned to it.
3.1.6 Segments
Logically, the Large Object system splits each object into one or more segments to
allow storage in the manner determined by the database administrator. Elsewhere in
this document, segment sizes are also referred to as powers of two. For example, the
diagram in the previous section, depicted segments length of 512 bytes up to 1
megabyte – these could also be represented as Powers of two from 9 to 20.
3.1.7 Parms
The most important part of the system to the administrator or performance specialist
is the parameter table. This contains many values that can be adjusted to affect the
behaviour of the Large Object system. Appendix B contains a table of all available
parameters values and associated descriptions. As part of the Large Object installation
sample scripts are provided to accept user input and create default parameters. The
section on shell scripts provides more details of the sample initialization script
metaData.sh.
Parameters are held at BuddyGroup level making it possible to vary object storage
behaviour by adjusting parameter values for different BuddyGroups. When a
BuddyGroup is first created, its status is inactive until a child BuddySet has been
created. Parameters may only be changed whilst the BuddyGroup is inactive. An
API call is provided to allow parameters to be changed (see SetBuddyGroupParm
API).
Note: Once the BuddyGroup is active, parm values must not be changed, as the Large
Object system could become unstable or possibly inconsistent.
3.2 Core APIs
3.2.1 OpenBuddyGroup
Initialise and open all Buddy Sets within a specified Buddy Group. This API must be
called before any of the other core APIs, and may take some time as it performs all
the file open operations.
short OpenBuddyGroup (const char *pBuddyGroupName //
input
);
Return Value:
0 = Successful
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