|
|
|
|
|
|
Using Logging to Track Transactions
Logging is used to keep track of the progress of a 2-phase commit protocol. The information stored in the log is used to make sure a transaction is completed in the event of a network failure or machine crash.
To ensure completion of transactions across domains, domain gateways log the mapping between local and remote identifiers. Along with this information, the Domains transaction management facility records the decisions made during different phases of the commitment protocol, and any information available about the remote domains involved in the transaction. In the OSI TP case, the XAP-TP interface logs the information required for the recovery of the OSI TP protocol machine. The information is referred to as a blob (binary large object) and is kept in the same log record as the commit information to make recovery easier.
Domains log records have a different structure from the log records stored in the BEA Tuxedo system TLOG. TLOG records are fixed in size and are stored in a single page. Domains log records vary in size; more than one page may be required to store the record. The Domains logging mechanism, DMTLOG, has the capability of storing variable-size log records.
When a TMS is the superior of a domain gateway group, the BEA Tuxedo TLOG is still required to coordinate the commitment.
How Logging Works
Logging is performed by the GWADM administrative server. The request for a log write is made by the GWTDOMAIN process, but the actual log write is performed by the GWADM process.
You must create a log called DMTLOG for each domain gateway group. The DMTLOG files are defined in the DM_LOCAL_DOMAINS section of the DMCONFIG file. To create a DMTLOG file, add an entry for the DMTLOGDEV parameter:
DMTLOGDEV=string
where string is the name of the log file. In addition, you cam set one or both of the two optional parameters:
For more information, refer to DMCONFIG(5) in BEA Tuxedo File Formats and Data Descriptions Reference.
Administrators also have the option of using the run-time administration utility (DMADMIN) to create a DMTLOG. For more information, refer to dmadmin(1) in BEA Tuxedo Command Reference.
If a DMTLOG has not been created when a domain gateway group is booted, the gateway server automatically creates the log, based on information in the BDMCONFIG file.
Until a logging device is specified in the BDMCONFIG file, a Domain gateway group cannot process requests in transaction mode and the gateway group cannot offer the TMS service.
To coordinate the commit protocol, Domains gateways require the following two log records:
When a transaction has been committed on all machines, these logs for the transaction are removed.
When the OSI TP protocol is being used, two types of heuristic records are logged:
Heuristic log records persist until they are explicitly removed by the administrator. This persistence is required to provide the correct information during recovery after a crash, and to provide diagnostic information for administrators.
The administrator uses the forgettran command (run with tmadmin(1)) to remove heuristic records when they are no longer needed.
|
|
|
|
|
|
Copyright © 2000 BEA Systems, Inc. All rights reserved.
|