Methods to estimate the size of a journal receiver
You can estimate the effect that a journal receiver has on auxiliary storage.
The actual auxiliary storage used will be somewhat larger because the system writes additional entries for such actions as opening and closing objects, unless you omit open and close journal entries when you start journaling for database physical files or integrated file system objects.
The first method to estimate the size of a journal receiver is to use a journal receiver calculator. The Journal receiver calculator provides an easy way for you to estimate the size of your journal receiver without setting up journaling.
The calculator assumes the following:
- You are journaling after-images only.
- You are using a single journal receiver for an entire day's transactions.
- You are journaling database physical files only. It does not include estimates for access path journaling, integrated file system objects, data areas, data queues, or user-created entries.
- You are not minimizing entry-specific data for the files.
Another method for estimating the size of the journal receiver is to run a test. This method is more accurate because it includes all journal entries. Additionally, this method will work for any object type which can be journaled, not just database physical files unlike method one. To use this method, either have journaling set up already or set it up.
If you are already using journaling, skip steps 1 and 2 below. Instead, issue a Display Journal Receiver Attributes (DSPJRNRCVA) command before the time period so you can compare sizes from the beginning of the period to the end.
This method assumes that the same receiver is used during the whole test. If there is a change journal to attach a new journal receiver during the test, include the sizes of all the receivers.
- Set up journaling by creating the receiver and journal.
- Start journaling for all the objects that you plan to journal.
- Choose a time period (1 hour) with typical transaction rates.
- After one hour, use the Display Journal Receiver Attributes (DSPJRNRCVA) command to display the size of the receiver.
- Multiple the size by the number of hours that your system is active in a day.
Parent topic:
Planning for journal use of auxiliary storageRelated concepts
Functions that increase the journal receiver size Minimized entry-specific data for journal entries Threshold (disk space) for journal receiversRelated tasks
Journaling database physical files (tables) Journaling integrated file system objects Setting up journaling Starting journalingRelated reference
Display Journal Receiver Attributes (DSPJRNRCVA) commandRelated information
Journal receiver calculator