Release 10.1C: OpenEdge Replication:
User Guide


Calculating fixed after-image extent size

Following are two examples that illustrate how to calculate the source after-image extent sizes and total capacity when using fixed after-image extents. The calculated after-image extent size and total after-image capacity are shown in bold in the last two rows of Table 2–3 and Table 2–4.

After-image extent sizing based on hourly data

After the total after-image data written for four, separate one-hour periods are determined, the sizing calculations described in Table 2–3 are performed.

Table 2–3: After-image extent sizing calculations (hourly data) 
Description
Measurement/estimate
Average after-image data generated in one typical work hour
72.5MB = average of the following:
  • 70MB in hour 1
  • 67MB in hour 2
  • 79MB in hour 3
  • 74MB in hour 4
OpenEdge Replication after-image overhead
50%, or 1.5 multiplier
Number of processing hours during a typical workday
16 hours per day
Number of processing hours during the typical workweek
80 (16 hours per day x 5 days)
Estimate of after-image data generated in one day

1,160MB, or 1.13GB
(72.5MB x 16 hours per day)

Estimate of after-image data generated in one workweek
5,800MB, or 5.66GB
(1,160MB x 5 days)
Estimate of after-image data generated in one hour with OpenEdge Replication overhead
109MB (72.5MB x 1.5)
Estimate of after-image data generated in one day with OpenEdge Replication overhead
1,740MB (1,160MB x 1.5)
Estimate of after-image data generated in one workweek with OpenEdge Replication overhead
8,700MB (1,740MB x 5 days)
Single fixed after-image extent size
450MB (109MB x 4 hours)
Total number of after-image extents necessary to handle one week of processing
19 extents (8,700MB / 450MB)

After-image extent sizing based on weekly data

Using the total size of after-image extents for one full workweek, the sizing calculations described in Table 2–4 are performed.

Table 2–4: After-image extent sizing calculations (weekly data) 
Description
Measurement/estimate
Total after-image data generated in one typical week
15,000MB, or 14.6 GB
OpenEdge Replication after-image overhead
50%, or 1.5 multiplier
Number of processing hours during a typical workday
16 hours per day
Number of processing hours during the typical workweek
112 hours
(16 hours per day x 7 days)
After-image data generated in one hour
134MB
(15,000MB / 112 hrs in week)
After-image data generated in one day
2,144MB, or 2.09GB
(134MB x 16 hours)
Estimate of after-image data generated in one hour with OpenEdge Replication overhead
201MB (134MB x 1.5)
Estimate of after-image data generated in one day with OpenEdge Replication overhead
3,216MB, or 3.14GB
(2,144GB x 1.5)
Estimate of after-image data generated in one workweek with OpenEdge Replication overhead
22,512MB (3,216MB x 7 days)
Single fixed after-image extent size
804MB (201MB x 4 hours)
Total number of after-image extents necessary to handle one week of processing
28 extents (22,512MB / 804MB)


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