Product Environment 9-45
Two-Phase Commit and Logical Log Records
TABLOCKS
TheTABLOCKS logical log record can be written by either a coordinator or a
participantOnLine database server. It is associated with either a BEGPREP or
aPREPARE record and contains a list of the locked tblspaces (by tblspace
number) held by the transaction. (Within theIBM Informix STAR
environment, transactions, not database server processes, are shown as the
owners of locks.)
Theoutput from tblog contains three fields: type; number of locks, expressed
as an integer; and locked tblspace number, expressed as a hexadecimal. (If
youconvert the hexadecimal value to an integer, the result is the value stored
as partnum in thesystables system catalog table.) The output appears as
follows:
TABLOCKS number_of_locks hex_tblspace_number
HEURTX
TheHEURTX logical log record is written by a participant OnLine database
serverto record a heuristic decision to roll back the transaction. It should be
associatedwith a standard ROLLBACK record indicating that the transaction
was rolled back.
The output fromtblog contains two fields: type and a heuristic flag,
expressed as a hexadecimal. The value of the flag is always one. The output
appears as follows:
HEURTX 0x01
ENDTRANS
TheENDTRANS logical log record is written by both the coordinator and
participant OnLine database servers to record the end of the transaction.
ENDTRANSinstructs OnLine to remove the transaction entry from its shared-
memory transaction table and close the transaction.
In the coordinator logical log, eachBEGPREP that results in a committed
transaction is paired with anENDTRANS record. If the coordinator ’s final
decision is to roll back the transaction, noENDTRANS record is written.
In the participant logical log, eachENDTRANS record is paired with a corre-
sponding HEURTX record.