iX V6.5 (30391-90011)

Chapter 5 241

TurboIMAGE/XL Library Procedures

DBXUNDO

5-10 Procedure call information. Refer to "Library Procedure

Error Messages" in appendix A for a description of this

information.

textlen

is an integer equal to the number of halfwords to be logged from the

text

parameter, or is a negative integer equal to the number of bytes. Length

can be zero.

Discussion

DBXUNDO is called to dynamically roll back a sequence of TurboIMAGE/XL procedure

calls that completed successfully inside a dynamic transaction. The beginning of such a

sequence is designated by a previous call to DBXBEGIN. DBXUNDO cannot be called to roll

back a transaction started by DBBEGIN or if the database is enabled for AUTODEFER.

Logging and DBRECOV are not needed with dynamic transactions, because the database can

be recovered dynamically. However, if the calling process is logging, DBXUNDO causes a

record to be written to the log ﬁle to identify the transaction in the event it needs to be

recovered.

CAUTION

After DBXUNDO is called, the current record pointer, current path, current list,

and chronological order prior to the call to DBXBEGIN may not be restored.

DBXUNDO cannot be called to roll back a transaction started by DBBEGIN. DBXUNDO returns

an error condition if it is called without a prior matching call to DBXBEGIN. DBXEND is not

necessary after DBXUNDO. DBXUNDO rolls back the entire transaction, and then

transactions continue according to the logic of the program. In general, DBXUNDO or DBXEND

must be the last intrinsic for a dynamic transaction to be executed. It designates the end of

that dynamic transaction.