Possible Replay Task Failures

When the RPG receives a request for a product (either via a One-Time Request (OTR) or Radar Multi-Request (RMR), hereafter referred to as simply an OTR) and the requested product has not been generated, the product is generated using data from the current VCP, if possible. If data for the current VCP is not yet available, data from the previous VCP is used.

When data from the previous VCP is used for an OTR, a "replay" task is used to generate the product. Not all products have an associated replay task.

When AVSET and SAILS are both active and the VCP termination angle, as determined by AVSET, is changing, an OTR may cause a replay task failure. This occurs if the location of the SAILS cut changes (due to the AVSET termination angle changing) between the previous and current VCPs.

Several very specific events must occur before a replay task will fail:

• SAILS and AVSET must be active
• AVSET must change the termination angle on the current VCP
• The termination angle change must have changed the location of the SAILS cut in the VCP
• An OTR must be received by the RPG for a product that:
  1. has not already been generated
  2. cannot be generated using data from the current VCP
  3. is for an elevation angle that has an elevation index that was the SAILS cut on the previous VCP

What is an elevation index? Internally, the RPG uses an "RPG elevation index" with each elevation slice being a single index number. In VCP 12 or 212, the 0.5 cut is elevation index 1. The 0.9 cut is elevation index 2. The 1.3 cut is elevation index 3, and so on. The SAILS cut receives an elevation index based on where it occurs in the VCP.

The replay task failure is only seen when the elevation index for the requested product on the current VCP is the SAILS cut on the previous VCP.

For Example:

• An OTR for a 4.0 SRM is made and the product is not already generated
• Based on the termination angle, the 4.0 slice is elevation index #8
• The current VCP is at the 0.9 angle, so data from the previous VCP is used via the replay_srmrmrv task
• In the previous VCP, elevation index #8 is the SAILS cut
• In this case, the replay_srmrmrv task will fail

In addition to AVSET, there is another way for the location of the SAILS cut within a VCP to change. Build 14 added Auto-PRF functionality to SZ-2 VCPs (211, 212, & 221). To maintain the 64 pulses/radial required for SZ-2, the antenna scan rate is adjusted slight to either go faster (when the PRF increases) or slower (when the PRF decreases). Although this is a small change to scan rate, it can impact where the "middle" of the volume scan is and, therefore, the location of the SAILS cut within the VCP.

So, for this second possibility, there are still several very specific events that must occur before a replay task will fail:

• SAILS must be active in VCP 212 (AVSET could be on or off)
• AUTO-PRF must change the PRF on the current VCP enough to changed the location of the SAILS cut in the VCP
• An OTR must be received by the RPG for a product that:
  1. has not already been generated
  2. cannot be generated using data from the current VCP
  3. is for an elevation angle that has an elevation index that was the SAILS cut on the previous VCP

What if a Task Fails:

If one of the "replay" tasks fail, the following will be seen on the MSCF:

• On the main RPG HCI, the RPG box will turn yellow
• Alarms messages will be seen in the Status Log and a save log will be generated
• The message "Replay Request But Data Not Needed?" may also be seen in the Status Log
• No OTRs will be generated for the specific product via the replay function

To clear the failed task, place the RDA into Standby and then select "Startup" from the RPG Control window. After the RPG software restarts and the task failure clears, place the RDA back into Operate.

Note: This has been corrected in RPG Build 15.0 which is currently scheduled to deploy in November 2014.