Hi Jerry,
Unfortunately, the restriction is not currently in the manuals. This morning I have opened a new documentation change request (CR), 745042 to have the restriction added to the Reference Manual Commands entry for Unmount.
There is also an existing open feature request CR 356151, to either do away with the restriction or limit it to databases that are on devices that are actually being mirrored. This is currently seen as a low-priority issue and isn't being worked on, but it hasn't been rejected either.
Within about 24 hours, you should be able to see both CRs on the sybase.com "solved cases" web page http://search.sybase.com/search/simple.do?mode=sc by clicking the "change requests" box and searching for the CR numbers.
I can, however, demonstrate that the configuration setting does prevent using Unmount Database even on a database on an unmirrored device:
1> select @@version 2> go ------------------------------------------------------------------------------- ---------------- Adaptive Server Enterprise/15.7/EBF XXXXX SMP SP110 /P/Sun_svr4/OS 5.10/asecarina/3488/64-bit/FBO/Sun Jul 7 10:06:45 2013 [Note: this is on the internal nightly build of the dataserver from July 7th ] 1> disk init name = "datadev2", physname = "/work/releases/carina/data/datadev2", size = "50M" 2> go 1> create database mountdb on datadev2 = 24 2> go CREATE DATABASE: allocating 1536 logical pages (24.0 megabytes) on disk 'datadev2' (1536 logical pages requested). Database 'mountdb' is now online. 1> unmount database mountdb to "/work/my_manifest_test" 2> go 1> mount database all from "/work/my_manifest_test" 2> go Started estimating recovery log boundaries for database 'mountdb'. Database 'mountdb', checkpoint=(866, 79), first=(866, 79), last=(866, 79). Completed estimating recovery log boundaries for database 'mountdb'. Started ANALYSIS pass for database 'mountdb'. Completed ANALYSIS pass for database 'mountdb'. Started REDO pass for database 'mountdb'. The total number of log records to process is 1. Completed REDO pass for database 'mountdb'. Recovery of database 'mountdb' will undo incomplete nested top actions. Started recovery checkpoint for database 'mountdb'. Completed recovery checkpoint for database 'mountdb'. Started filling free space info for database 'mountdb'. Completed filling free space info for database 'mountdb'. Started cleaning up the default data cache for database 'mountdb'. Completed cleaning up the default data cache for database 'mountdb'. MOUNT DATABASE: Completed recovery of mounted database 'mountdb'. 1> sp_configure "mirroring" 2> go Parameter Name Default Memory Used Config Value Run Value Unit Type ------------------------------ ----------- ----------- --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- ------------------------ --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- ------------------------ -------------------- -------------------- disable disk mirroring 1 0 1 1 switch static (1 row affected) (return status = 0) 1> sp_configure "disable disk mirroring", 0 2> go Parameter Name Default Memory Used Config Value Run Value Unit Type ------------------------------ ----------- ----------- --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- ------------------------ --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- ------------------------ -------------------- -------------------- disable disk mirroring 1 0 0 1 switch static (1 row affected) Configuration option changed. Since the option is static, Adaptive Server must be rebooted in order for the change to take effect. Changing the value of 'disable disk mirroring' does not increase the amount of memory Adaptive Server uses. (return status = 0) 1> shutdown 2> go Server SHUTDOWN by request. ASE is terminating this process. CT-LIBRARY error: ct_results(): network packet layer: internal net library error: Net-Library operation terminated due to disconnect bret-sun2% bret-sun2% startserver -f RUN_$DSQUERY [snip] 00:0002:00000:00001:2013/08/12 09:27:06.24 server Recovery complete. 00:0002:00000:00001:2013/08/12 09:27:06.35 server ASE's default unicode sort order is 'binary'. 00:0002:00000:00001:2013/08/12 09:27:06.35 server ASE's default sort order is: 00:0002:00000:00001:2013/08/12 09:27:06.35 server 'bin_iso_1' (ID = 50) 00:0002:00000:00001:2013/08/12 09:27:06.35 server on top of default character set: 00:0002:00000:00001:2013/08/12 09:27:06.35 server 'iso_1' (ID = 1). 00:0002:00000:00001:2013/08/12 09:27:06.35 server Master device size: 580 megabytes, or 296960 virtual pages. (A virtual page is 2048 bytes.) 00:0002:00000:00001:2013/08/12 09:27:06.99 kernel Setting console to nonblocking mode. 00:0002:00000:00001:2013/08/12 09:27:06.99 kernel Console logging is disabled. This is controlled via the 'enable console logging' configuration parameter. bret-sun2% isql -Usa Password: 1> unmount database mountdb to "/work/my_manifest_test2" 2> go Msg 14543, Level 16, State 1: Server 'rel1572_bret_sun2', Line 1: UNMOUNT DATABASE command is not allowed when mirroring is enabled. 1>