dbs/ora/array_buf_size is a SAP Parameter attribute which is used to control Size of input/output buffer used for array operations information. This is available within R/3 SAP systems depending on the version and release level.
Below is the standard documentation available and a few details of the attributes values .
This parameter defines the size of a data area with which the input and
output values of an SQL statement are transferred to the Oracle
database. It influences in particular the maximum number of records that
are brought into the database with an array operation (such as array
insert) or that are read from there (array fetch). The larger the
selected value, the more records can be transferred to or from the
database with a single database operation. However, the Oracle network
software also partitions the data to be transported again, so that
increasing the value may not necessarily lead to a reduction in network
traffic.
The default value of the parameter is -1. This means that an internal
system default value is used for the size of the array buffer. This
default value should only be changed in consultation with SAP.
See SAP Parameter Documentation for full SAP documentation for this profile parameter.