HP 3000 Manuals

HP Transact Reference Manual

Appendix A  Flowcharts of File and Database Operations 

Flowcharts of File and Database Operations 

The flowcharts in this appendix provide an overview of the major
database, file system, and VPLUS intrinsic calls issued by Transact to
perform data management operations.  The charts provide a basic
understanding of the steps that occur when a verb executes.  However,
they should not be viewed as definitive explanations of all events caused
by a given verb.

Calls that are shown in brackets occur only when circumstances dictate.

Rules that govern use of calls for locking, unlocking, and opening files
are as follows;[REV BEG]

DBLOCK          If a database or data set is not already locked, DBLOCK
                is applied according to the rules given in Table 6-2 (if
                optimized locking is used) or Table 6-4.[REV END]

DBUNLOCK        This call is applied in either of the following
                circumstances:

                If the current verb invoked the original lock; if the
                database or data set is locked; and if the lock option is
                not used

                OR

                The last record has been accessed for a multiple record
                operation (for example, CHAIN, SERIAL, RCHAIN, or
                RSERIAL) when the lock option is used. 

FOPEN           This call is used if the file is not already open.[REV
                BEG]

FLOCK           This call is used if the file is not already locked,
                according to the rules given in Table 6-4.[REV END]

FUNLOCK         This call is applied if the program is at the same
                instruction which invoked the FLOCK. 

Separate flowcharts are included for each verb to describe database and
file access.

Flowcharts are given for the following verbs:

DELETE     - for a data set or a KSAM file operation

FIND       - for a data set or a KSAM or MPE file operation

GET        - for a data set or a KSAM, MPE, or VPLUS file operation

OUTPUT     - for a data set or a KSAM or MPE file operation

PATH       - for a data set or a KSAM file operation

PUT        - for a data set or a KSAM, MPE, or VPLUS file operation

REPLACE    - for a data set or a KSAM or MPE file operation

SET        - for a VPLUS file operation

UPDATE     - for a data set, or a KSAM, MPE, or VPLUS file operation

MPE/iX 5.0 Documentation