Reading my Journal

All,

Ever had a situation where data was being erroneously written, or simply disappeared and you had no idea why.  For anyone with a journaled database on the IBMi this will be an all to familiar issue.  A commitment control boundary may undo your updates, or the data simply doesn't look right as it is being updated elsewhere in your call stack, far away from the code area you are presently maintaining.

When this happens to me I usually like to review the entries in the journal and analyse the database I/O data to get a feel for what is happening.

So how do I go about doing this.....

Firstly I would identify the journal that is being used.  This may change from time to time so it is best to check each and every time you perform these steps.  Do a WRKOBJ for the library and main file you are trying to track entries for.

WRKOBJ OBJ(DATALIB/TARGETFILE)

Take option 8=Display Description and page down three times or do a DSPFD for the given file and search of the Journal name from the output.

Now you know the journal.  Perform the action(s) you wish to monitor for and note the times.  (start and Finish)

You can then extract this data from the journal using the DSPJRN command.  Below is an example of isolating the entries in a particular environment.  I have gone for all files in library MSLTSTDTA in this example but there are plenty of filtering options.  I then chose to output the resultant data into a file so that I could query it more easily.

DSPJRN JRN(TB_JRN/JRN0103000) FILE((DATALIB/*ALL)) FROMTIME(280222 074200) TOTIME(280222 074300) OUTPUT(*OUTFILE) OUTFILE(LDARE/LD_JOURNAL).  The OUTFILE keyword is optional but will help if you want to perform some queries are a saved dataset.

Please note that the date and time parameters are particularly important as this can take a while to extract otherwise.  Just this small sample took a few seconds interactively.  If querying for more, you might want to consider submitting the task.

The resultant data file is formatted as follows:-

 

The main item to look for is the 'Entry Type'.  These codes identify when data is inserted, updated or deleted from the database table as well as if it is rolled back.

The table below are the main ones that I refer to.  All of these are for Journal Code 'R' - Operation on Specific Record. For a full list of the items covered by journaling see this link

https://www.ibm.com/docs/en/i/7.2?topic=information-journal-code-descriptions

 

Entry Code	Description
BR	Before-image of record updated for rollback operation
DR	Record deleted for rollback operation
PT	Record added to a physical file member. If the file is set up to reuse deleted records, then you may receive either a PT or PX journal entry for the change
PX	Record added directly by RRN (relative record number) to a physical file member. If the file is set up to reuse deleted records, then you may receive either a PT or PX journal entry for the change
UB	Before-image of a record that is updated in the physical file member (this entry is present only if IMAGES(*BOTH) is specified on the STRJRNPF command)
UP	After-image of a record that is updated in the physical file member
UR	After-image of a record that is updated for rollback information

 For a full list of journaling codes you can use this link within the IBM i documentation.

 https://www.ibm.com/docs/en/i/7.2?topic=information-all-journal-entries-by-code-type