Page 232 - Kỷ yếu hội thảo khoa học lần thứ 12 - Công nghệ thông tin và Ứng dụng trong các lĩnh vực (CITA 2023)

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technologies like Flash memory are shown like the low power consumption, the fast
access, and the long write endurance. The concept of "univeral memory" is also
introduced. univeral al memory allows flexible partitioning of the memory for code and
data: the same type of memory can be used for both data and program storage that are
"traditionally" kept in separate memories: RAM for data and flash or ROM for program
storage.
SQLite[6] is an in-process library that implements a self-contained, serverless,
zero-configuration, transactional SQL database engine. Unlike most other SQL
databases, SQLite does not have a separate server process. SQLite reads and writes
directly to ordinary disk files. A complete SQL database with multiple tables, indices,
triggers , and views, is contained in a single disk file.
Prior to making any changes to the database file, SQLite first creates a separate roll-
back journal file[7] and writes into the rollback journal the original content of the data-
base pages that are to be altered. The idea behind the rollback journal is that it contains
all information needed to restore the database back to its original state.
Creating rollback journal files causes a lot of flash memory operations leading to
reduction of overall performance of SQLite and Nand flash memory. Therefore, a new
solution should be proposed to address above problem. Next, section 3 will present the
design of the new solution.

3 The design and implementation of BBS

3.1 The design of BBS
This section presents a novel buffer based scheme and a hybrid storage system for
SQLite on flash memory using FRAM, called BBS, to efficiently store the journal file
when inserting, updating or deleting data from SQLite database. Its objective is to
significantly reduce the overhead of writing journal file onto flash memory when
database is modified. In order to achieve the aforementioned goal, we deploy a hybrid
storage of FRAM and flash memory to store journal file and data. FRAM has no
erase-before-write feature, so it is used to store journal file while flash memory is used
to store data. Figure 1 shows the architecture of BBS comprising all components of a
traditional androi system, hybrid driver and a hybrid storage of FRAM and flash
memory.
The hybrid driver module basically manages and decides which storage medium is
used to write data onto. If the journal file is created or modified, hybrid driver will flush
data of journal file to FRAM driver. On the other hand, the modified data will be flushed
to flash memory driver. FRAM driver and flash memory driver manage and write data
to FRAM and flash memory according to their policies.
FRAM is used in company with flash memory to improve the overall performance
of SQLite on Android smart phone system. Since data can be overwritten on FRAM, it
is able to avoid the limitation of erase-before-write of flash memory. Whenever journal
file is created, BBS writes the journal file onto FRAM instead of flash memory that the
conventional android systems do. This lead to a significant reduction of overhead of

CITA 2023 ISBN: 978-604-80-8083-9