iX V6.5 (30391-90011)

642 AppendixC

Database Design Considerations

activity on sorted chains to reading and updating (DBUPDATE).

• Do all or most of your locking at one level (database, data set, or data entry).

• If locking at the data entry level, do all or most of the locking using the same item in

each data set. Otherwise, performance will be the same as if you were locking at the

data set level.

• Avoid holding locks around a terminal read.

• Avoid beginning and ending logical transactions around a terminal read.

• All databases involved in a multiple database transaction must reside on the same

system.

• If transaction logging is used, the database administrator must ensure that

all

databases involved in a multiple database transaction adhere to the following criteria:

— Are enabled for logging.

— Log to the same log ﬁle.

— Are either enabled or disabled for roll-back recovery.

— Are either enabled or disabled for MUSTRECOVER.

• For remote database access (applications and databases are not on the same system),

the application's node, the database node, and all intermediate nodes where a multiple

database transaction is routed must be on TurboIMAGE/XL version C.04.00 or later.