Reduce the size of journal entries by methods such as journaling after-images only, or specifying certain journaling options including the Fixed Length Data (FIXLENDTA) option on the Create Journal (CRTJRN) and Change Journal (CHGJRN) commands.
Methods to reduce the storage needed for journaling are as follows:
- Journal after-images only
- Unless you are using commitment control, after-images are sufficient for your recovery needs. When you start journaling, the default is to journal after-images only. You can use the Change Journal Object (CHGJRNOBJ) command to stop journaling before-images without ending journaling for that object.
- Omit the journal entries for open, close or force operations to journaled objects
- You can omit these journal entries with the OMTJRNE parameter on the Start
Journal Physical file (STRJRNPF) or Start Journal (STRJRN) command.
For database files (tables), you can select Exclude open and close
entries when you start journaling with iSeries™ Navigator. For integrated file
system objects, ensure that Include open, close, and synchronization
entries is not selected when you start journaling with iSeries Navigator.
You can also use the CHGJRNOBJ command to start omitting
these journal entries for objects that you are currently journaling.
Omitting
these journal entries can have a noticeable effect on both space and performance
if an application opens, closes, or forces objects frequently.
Also, any time one looks up an object in a directory, that can cause an open
and close entry to occur for that directory. This can be a lot of additional
journal entries if they are not omitted from the directory objects. However,
if you omit the journal entries for opening and closing objects, you cannot
perform the following tasks:
- Use open and close boundaries when applying or removing journal changes (the TOJOBO and TOJOBC parameters).
- Audit which users open particular objects.
- Swap journal receivers, save them, and free storage more frequently
- Frequently saving and freeing storage for journal receivers help reduce the auxiliary storage that the receivers use. However, moving journal receivers off-line increases your recovery time because receivers have to be restored before journal changes can be applied.
- Specify receiver size options that can decrease journal receiver size
- Specifying the following receiver size options can help reduce journal
receivers size:
- Remove internal entries. This causes the system to periodically remove internal entries that it no longer needs, such as access path entries.
- Minimize the fixed-length portion the journal entry. This causes the system
to no longer deposit all of the data selectable by the FIXLENDTA parameter
in the journal entry, thus reducing the size of the entries. However, if you
require this journal entry information for audit or other uses, you cannot
use this storage saving technique. Additionally, it reduces the options available
as selection criteria used on the following commands and API:
- Display Journal (DSPJRN) command
- Receiver Journal Entry (RCVJRNE) command
- Retrieve Journal Entry (RTVJRNE) command
- Compare Journal Images (CMPJRNIMG) command
- Apply Journaled Changes (APYJRNCHG) command
- Apply Journaled Changes Extend (APYJRNCHGX) command
- Remove Journaled Changes (RMVJRNCHG) command
- Retrieve Journaled Entries (QjoRetrieveJournalEntries) API
- Minimized entry-specific data for journals
- Minimizing entry-specific data allows the system to write data to the journal entries in a minimized format.
- Select the fixed-length options for data carefully
- Fixed-length options can quickly increase the size of your journal receiver. The journal receiver calculator can help you determine the effect of fixed-length options on your auxiliary storage.
- If you are journaling a physical file, specify SHARE(*YES) for the file.
- You can do this using the Create Physical File (CRTPF) command or the Change Physical File (CHGPF) command. The system writes a single open and close entry regardless of how often the shared open data path (ODP) is opened or closed within a routing step.