User Guide

SAP AG November 2002
Transaction
A transaction is a series of database operations that form a unit with regard to data backup
and synchronization.
Transactions are closed with COMMIT [Page 12 ]9 or ROLLBACK [Page 14 ]7 .
See also:
Reference Manual: SAP DB 7.4, Section Transaction [See SAP DB Library]
Lock behavior [Page
113]
Transaction file [Page
152]
Transaction list [Page 152]
Transaction File
The transaction file is an internal database file to which the data of all open transactions
[Page 152] is written at the time of a savepoint [Page 149]. The transaction file is stored in the
data area [Page
131].
During a restart [Page 146], the log reader [Page 50] uses this transaction file to regenerate
the transaction list [Page
152].
Transaction List
The transaction list is an internal database list of all open modifying transactions. The
transaction list is located in the main memory.
All modifying transactions are globally available in the database via this transaction list. The
transaction list contains a transaction entry for each transaction [Page 152]. This transaction
entry contains references to any redo [Page 44] and undo log entries [Page 44] that may
exist.
During a restart [Page
146], the log reader [Page 50] uses the transaction file [Page 152] to
regenerate the transaction list.
UNICODE
Data types such as CHAR ASCII and CHAR EBCDIC are mainly suited to English and central
European languages. With other character sets, a code attribute is usually used for these
data types. This code attribute uses a different presentation code to ASCII and EBCDIC, even
for internal storage in the database system. This causes problems if you want to access these
database systems using a different character set, or if you want to exchange data between
database systems with different character sets.
You can avoid these problems by using internal character coding in accordance with
UNICODE. Internally, the UNICODE data is stored in UTF-16/UCS-2 format. In UTF-16/UCS-
2 format, all characters are two bytes long.
SAP DB is able to display various presentation codes in UNICODE format (UNICODE code in
line with ISO 10646, page 1).
User Manual: SAP DB 152