Problems with multiple entries in vB's Scheduled Tasks

For the past few weeks we've had vBulletin set to generate sitemaps at 4am. This was a good time for two reasons - because most of the traffic on our forums will have ceased by that time, and because Google seems to enjoy retrieving our sitemap files at 5am.

We noticed that Google was, in fact, retrieving our sitemaps twice daily, around 5am and again at around 5pm.

It's a bit silly for Google to be downloading the same old sitemap a second time, so we decided to instead exploit the opportunity by regenerating the sitemap just prior to the second download time.

We now have two entries in vBulletin's scheduled tasks listing for 4am and 4pm:

00 4 * * * vBSEO - Create Google/Yahoo Sitemap 28 Jan 2006 4:00 AM
00 16 * * * vBSEO - Create Google/Yahoo Sitemap 28 Jan 2006 4:00 PM

However, whilst both tasks are successfully started, only the second task ever completes. This is an excerpt from our scheduled tasks log:

11238 vBSEO - Create Google/Yahoo Sitemap 16:00, 27th Jan 2006 Google Sitemap [Started]

11240 vBSEO - Create Google/Yahoo Sitemap 16:00, 27th Jan 2006 Google Sitemap Created

...

11229 vBSEO - Create Google/Yahoo Sitemap 04:00, 27th Jan 2006 Google Sitemap [Started]

Note that the 4am sitemap is never actually created. Additionally, our sitemap reports list shows only the 4pm generation.

The process ID numbers also appear to be out of order, but I am not certain that this is of any significance.

Hello!

There is no direct connection between google notification and sitemap download (i.e., it doesn't work like ping->immediate download).
In fact, if you will manually submit your sitemaps to google webmaster account, you can turn off the notification option and google will still be downloading your sitemap.

Thanks for your prompt response Oleg, but I think you may have misunderstood my query.

Once I had submitted our sitemaps to Google manually, we noticed that Google was consistently downloading them at 5am and and again at 5pm every day - so we did turn the Google notification option off. That's all fine.

What I want to know is why vB's scheduler appears to have difficulty running the sitemap generation script more than once in a 24hr period (or when there are multiple entries defined for it in the scheduled tasks list). We want our sitemaps to be generated at both 4am and 4pm, yet the generation script appears to only function correctly on the second invocation.

Ah, yes - I missed your point, sorry

Did you tried to leave only one entry for 4am and check if it works?

Yes - that is what we had initially.

It's only since we added the later task scheduled for 4pm that the earlier task started malfunctioning.

Is anyone able to provide assistance with this.

PM sent