rsdb/tbi_dir_entries is a SAP Parameter attribute which is used to control Number of directory entries for the table buffer 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 number of directory entries for the table
buffer. The number includes entries for all kinds of buffered tables
(fully buffered, generic buffered and single row buffered).
It replaces the profile parameters rttb/max_tables and
zcsa/db_max_buftab.
If rsdb/tbi_dir_entries is not set or the default value is not changed,
but
rttb/max_tables and zsca/db_max_buftab are set, for backwards
compatibility,
the number of directory entries is automatically calculated by the
following rule:
no entries = rttb/max_tables + zcsa/db_max_buftab
See SAP Parameter Documentation for full SAP documentation for this profile parameter.