Vector logging is a diagnostic tool that allows you to record the flow of data between CICS applications and a virtual terminal. It is designed to be used in a development environment to assist in the deployment and running of a generated Adapter service that includes Link3270 server adapters, as well as passthrough processing.
Vector logging can be set as an option when a flow is modeled in Service Flow Modeler. When the generated Adapter service is deployed, a record is written in the properties file to specify that vector logging should be performed for that specific Link3270 server adapter. Alternatively, if you want to turn vector logging on for a Link3270 server adapter that is already deployed, you can update the record for it in the properties file using the update job DFHMAMPF.
There are two levels of granularity that you can select for vector logging:
When the Link3270 server adapter is operational in the runtime environment, it writes to a vector log file called DFHMALVF. You can access the contents of the vector log file by dumping it using the provided sample JCL job DFHMAMVD. This job runs the dump utility DFHMAVUP, which formats the file so that you can read it to help with problem determination. The dump utility displays the records in chronological order.
If you switch vector logging on, the server adapter continues writing information until the file is full. When the file is full, vector logging stops, even if the server adapter has not finished request processing. If you apply APAR PK32131, the vector logging functionality has improved so that two files, DFHMALVA and DFHMALVB, are used to store vector logging information. One of these files is always active, and the other is either empty or contains old data. The Link3270 server adapter starts by writing vector logging data to DFHMALVA. When the file is full, the Link3270 server adapter swaps to continue writing information to DFHMALVB. When DFHMALVB is full, the server adapter moves back to writing to DFHMALVA, deleting the old content.
The benefit of using two files is that you can analyze the complete vector logging data for a server adapter. It is very unlikely that a server adapter would write enough data to fill both files, but if this does happen, the most recent data is always available.
Vector logging for passthrough processing is performed in the same way as the logging for Link3270 server adapters. The only difference is that the vector logging is handled by the Link3270 passthrough manager program DFHMALPT, as there is no Link3270 server adapter.
Passthrough processing does not use the properties file, so you must specify it in the DFHMAH2-VECTOR-LOGGING field of the DFHMAH2 header using Service Flow Modeler. When this field is included in the header, the Link3270 passthrough manager program writes vector logging information to the active vector log file.