Reduce the size of journal receivers by specifying minimized entry-specific data on the Create Journal (CRTJRN) and Change Journal (CHGJRN) commands.
If you have selected to use the MINENTDTA parameter for the journal, then some of your journal entries' entry-specific data will be minimized. The entries will only be minimized if the minimization technique will deposit a journal entry which is smaller in size than the complete entry would be. Use the Journal entry information finder to see which specific journal entry types can possibly be minimized. When the entry is minimized, the fixed-length portion of the journal entry will have the minimized entry-specific data indicator on. Currently, only data areas and database physical files can have their entry-specific data minimized.
Data area considerations
The layout of the data area entries which are minimized is exactly the same as the layout if the entry was not minimized. The only difference is that only the bytes which actually changed are deposited rather than depositing all the bytes on the change request. See Update data area journal entries for the entry layout of the change data area entries.
Database physical file considerations
The
layout of the minimized record changes entries is completely different than
the layout when the entry is not minimized. If MINENTDTA(*FILE) is used, the
data is not readable because sophisticated hash techniques are used in addition
to only operating on actual changed bytes. Additionally, the Null-value-indicators
field will be used, even if the file is not null capable, to provide additional
information that can be used by database operations. Therefore, if you want
to use the journal as an audit mechanism, you may not want to choose the MINENTDTA(*FILE)
option for database physical files since you will not be able to read the
actual change made.
If minimized journal entries are collected
on field boundaries using the MINENTDTA(*FLDBDY) option, the data within the
journal entries may be displayed in the recognizable record layout of the
file. When this option is used, fields that were not collected will display
default data and the null value indicator table will use a new value to indicate
which fields are showing the actual data versus which ones are showing default
data because the fields were not collected. A ‘9’ in the null value field
will indicate the data is not actual data and that it was filled in with default
data.
Even if the file is not null capable, the Null value indicators field is used to provide additional information that can be used by database operations. Therefore, if you want to use the journal for auditing purposes, you may want to use the *FLDBDY value on the Minimized entry specific data (MINENTDTA) parameter for the CRTJRN and CHGJRN commands discussed below.
View minimized entry-specific data
The
*FLDBDY value indicates that minimizing of record level changes should be
done on field/column boundaries for all files journaled to the specified journal.
Using the Display Journal (DSPJRN) command, entries are
viewable to the screen, an outfile, or printed output. If a journal entry
has been minimized on field boundaries, the value of 2 is returned in the
Minimized entry specific data field of the *OUTFILE and in the Min field of
the printed output. The RCVJRNE and RTVJRNE commands
can also be used to view entries that were minimized on field boundaries by
specifying *YES on the Format minimized data (FMTMINDTA) parameter. The QjoRetrieveJournalEntries API
can be used to view entries that were minimized on field boundaries by specifying
*YES for the Format minimized data (FMTMINDTA) key.