The Bishop of the Isles, not content with earlier extensions of the great cruciform cathedral church of St Eve and St Lilith on the Isle of Celyddon, has instructed his master masons to draw up plans for a monumental and grandiose scheme project to extend and enlarge the cathedral, to outdo even many of the great mainland cathedrals. It stands on a grand, elevated cathedral close above the castle that dominates that town and the islands, built in a mixture of Norman and early Gothic styles. The cathedral has an unusual retro-choir behind the high altar, beneath a great rose window. In the latest renovations, the cathedral close has been enlarged, double aisles have been added to the nave, the transepts have been extended with a new central tower over the crossing, and aisles have been added behind the choir, sanctuary and retro-choir. These now lead to an ambulatory around the the new apse, replacing the demolished Norman towers at the east end. Finally, work is proceeding to re-build the crypt to house the remains of the line of bishops and the chapter of the cathedral.

But little do the townspeople know that unseen forces are being disturbed on the old misty fell where the work to construct the cathedral is being carried out. Sinister forces have fled the high hell (known to locals as Y Crib) for the nearby, seeimingly barren, mysterious island of Manaw in the west, where the townspeople have long feared to tread since the plague wiped out its population two centuries ago. All is not as it seems. Something nefarious stirs there. For how much longer will the town be safe?

Come and see - before the peril grows too great! - the tombs of the two saints of the Hebrew Old Testament, the great spire and the four doors of the Tower of the Winds, the great rose window in the East, a pair of transept-chapels with the tomb of St Eve at the crossing, and a highly unusual interfaith retro-choir with the tomb of St Lilith beneath the floor. Wonder at the strange inscriptions and effigies. Changes have been made to the castle to secure the cathedral's defence from seafaring raiders and pirates. But perhaps the real enemy lies somewhere closer at hand...

YEngine is a more modern script engine than XEngine. It's main advantage is that it recovers memory from scripts, which XEngine does not do, according to the OpenSim documentation. Its syntax and error reporting is also supposed to be better (and is supposed to be closer to the standard syntax of the SL script engine). It is the default script engine from OpenSim and this means that we will needed to switch to it for a forthcoming upgrade if we are to follow standard developments in OpenSim (although XEngine will still be available). It makes made sense to perform a phased switchover (functionally an upgrade) to YEngine before doing a full upgrade in order to check to see whether anything breaks broke (and fix it). Consequently, we are starting started by moving empty regions like sea areas and little-used islands over to YEngine first and then we will moved the three most developed islands one by one. The hope is that the need to restart simulators will be less frequent once memory is recovered automatically by the script engine.

This experience has been so good that we wholeheartedly recommend that all grids switch to YEngine unless there is a very good reason not to do so. The only one that I can think of is those people who are writing scripts in C#, which YEngine does not support but XEngine does. This can't be very many people. Do NOT try to run both script engines at once. The performance problems are huge.

[Final edit at 2021-12-21 15:36]

All complete at 2021-12-21 15:29 GMT: all sea areas with 5122 island region Manaw, the 12802 large island region Rheged, the 2562 island regions Aeron, Gododdin, Celyddon & Annwfn: scripts fixed. See below for stats for minor script errors fixed.

Stats on compile errors at 2021-12-21 15:29 GMT:

  • Rheged: 1 (of 19 = ~5.3%. This script was probably already broken but this was experimental/test code.)
  • Manaw: 0 (of only 2 scripts here anyway! 0%)
  • Sea areas (6): 0 (of only 2 scripts each here anyway! 0%)
  • Gogoddin: 11 (of 1072 = ~1.0%)
  • Celyddon: 9 (of 1075 = ~0.8%)
  • Annwfn: 8 (of 896 = ~0.9%)


  • YEngine also has some improvements and additions that can simplify scripting, as documented on the OpenSim YEngine page.
  • The biggest challenge is concern was the three 2562 island regions Annwfn (home region), Celyddon & Gododdin. These are where all the major sights are and consequently lots of scripts that might possibly break here and there where YEngine syntax is stricter. We shall see how good our scripting standards are! Apparently our scripting standards are on the whole pretty good with some minor errors only!
  • The errors in the logs conveniently give prim name:script name and the vector coordinates of the prim, so it's quite easy to track down and fix these scripts. Perhaps some of them were already broken?
  • It does seem from these fixes that XEngine allowed many type errors to pass, possibly breaking expected behaviour in some cases (see points below on touch_* events).
  • The slow region start/restart caused by XEngine having to tediously convert all of the scripts into C# is avoided, meaning that regions come up much faster!
  • In fact, shutting down threads also seems faster, so the slow shutdown problem is also considerably improved!
  • Performance is noticeably improved: no doubt through much better thread management for scripts.
  • Initial monitoring (using top in Linux/Debian) shows a dramatically reduced memory imprint. If this is sustained then performance will be increased, which will be very high given that we have 32GB RAM on the server, and region restarts will no longer have to be performed once or twice daily! This could potentially open the door to running additional simulators, although there are no plans to do so at present after the recent addition of 6 new regions of various sizes on an additional simulator (1 new island and 5 sea areas).
  • Mostly these were very silly mistakes in scripting that XEngine ignored. None had significant security errors: e.g. all prevented use by groups where it should have been allowed is more restrictive rather than less). All examples so far have been touch_* events using llDetected* functions including a very few integers compared with TRUE where the word was mistakenly put in brackets as a string (which would have failed).
  • We are not including multiple similar errors in one script in these stats.
  • We ignored warnings about script-defined type declarations, which are numerous but do not prevent scripts running. On a further restart, these did not reoccur.

A new 512x512 island has been added to Ocean Grid, in a region called Manaw. For those with an interest in history and place names, this is the Welsh name for the Isle of Man and also of an ancient Brittonic or early Welsh kingdom near Edinburgh. Technically this demonstrates that varregions can have borders with regions of different sizes, which has been possible in OpenSim 0.9.x but was not recommended for previous versions.

At the time of writing the single parcel, which is in development, has the following description in Welsh and in English:

"Ynys fawr nad oes enaid byw arni. Gochelwch rhag y fampirod!
A large island without a living soul on it. Beware of the vampires!"

The same simulator has also now been used [2021-11-16] to run adjacent sea areas around the four original islands, the experimental region Rheged and the new island Manaw. Other than the sea areas, each of these are run on separate simulators. Simulator boundary crossing is more consistent and reliably faster between Manaw and the sea areas than it is between different simulators, which is perhaps not altogether surprising.

The total number of simulators on Ocean Grid is now 6 and the number of regions including the 5 sea areas is 11, up from the 4 original regions.

Perhaps it is appropriate for a grid called Ocean Grid that it now has more sea than land!

Note [2021-12-03] Some instability had been noticed for some time on the TLS regions using HTTPS including this one. It turned out to be a configuration problem where Monit was unable to test that the regions were online, including these ones and the large island Rheged, so was constantly re-starting them. This has now been resolved and they are working normally again. Their TLS certificates have also been renewed, as they were approaching expiry, but they had not expired and this was not the issue that was causing the problem.

The cruciform cathedral church of St Eve and St Lilith has been erected above the castle in a mix of Norman and early Gothic styles on the former high fell in Celyddon (known to locals as Y Crib), containing the tombs of the two saints of the Hebrew Old Testament. Come to see the great spire and the four doors of the Tower of the Winds, a great rose window in the East, a pair of transept-chapels with the tomb of St Eve at the crossing, and a highly unusual interfaith retro-choir with the tomb of St Lilith beneath the floor. Wonder at the strange inscriptions and effigies. Changes have been made to the castle to secure the cathedral's defence from seafaring raiders and pirates. But all is not as it seems. Something nefarious stirs nearby on a mysterious, seemingly barren isle in the west, where the townspeople fear to tread... Is the town safe?

You can now make in-world partnerships in Ocean Grid. Unlike in SL, you don't have to pay anything to do so!

This feature has been added using the code provided on GitHub by djphil, forked for improved English and some minor database settings here by Starflower Bracken.