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Applies to: Oracle Server-Enterprise Edition-Version: 8.1.7.4 to 11.2.0.2.0-Release: 8.1.7 to 11.2Generic UNIX when checking that the background process of the oracle instance does not exist, launch the database error: ORA-01081: "cannot start already-running ORACLE-shut it down first" causes this is Orphaned shared memory segments and semaphores did not get cleared properly from the last instance shutdown. During the last shutdown of an oracle instance, an isolated shared memory segment and signal are not cleaned up. The solution can use ipcs to find out the shared memory segment or signal. Use ipcrm to manually clear orphaned shared memory segments (orphaned shared memory segment) and semaphores (semaphore) [root@rac01] # ipcs-a-Shared Memory Segments-key shmid owner perms bytes nattch status 0x4e44b264 557069 oracle 287309824 25 0xd06e774c 524302 oracle 640 132120576 16 -Semaphore Arrays-key semid owner perms nsems 0x000000a7 0 root 600 1 0x2e7fd0cc 131073 oracle 64044 0x334b5294 262146 oracle 640154 [root@rac01] # ipcs-m-Shared Memory Segments-key shmid Owner perms bytes nattch status 0x4e44b264 557069 oracle 640 287309824 25 0xd06e774c 524302 oracle 640 132120576 16 ipcs: check the allocated shared memory ipcrm: manually release the shared memory segment to obtain ipc information: ipcs [- m |-Q |-s]-m outputs information about shared memory (shared memory) Information-Q output information about information queue (message queue)-s output information about "semaphore" (semaphore)-a uses all printing options. (shorthand for-b,-c,-o,-p, and-t) Example: ipcrm-m shmid number-for shared memory ipcrm-s semid number-for semaphores ORShutdown all the instances belonging to the user. Next, run "ipcs-b" to find the remaining IPC facilities, owned by the same user, and remove them. However, if you're running multiple production instances, this may not be acceptable. In the case of multiple instances. Run ipcs-a > / tmp/ipcs_before.out 2. Use SQL*Plus to connect all instances to make a simple query select * from dual; 3. Run ipcs-a > / tmp/ipcs_after.out 4 again. Compare "/ tmp/ipcs_before.out" and "/ tmp/ipcs_after.out" files to find shared memory segments that have not changed in LPID: LPID shows the process ID that appends or separates shared memory segments in the final process, because, by executing a query in each living instance, you will refer to the shared memory segments that belong to each instance. But the uncovered shared memory segment will become an isolated 5. After identifying the orphaned shared memory segments, you can find the orphaned semaphores by locating the semaphores with the same value of CTIME in "ipcs-a" output as the value of CTIME for the orphaned shared memory segments: CTIME shows the time when the associated entry was created or changed. After identifying the isolated shared memory segment, we can use the output of ipcs-a to determine the signal with the same CTIME value to find the isolated shared memory segment as the related isolated shared memory segment NOTE: This step may not be necessary on the platforms implementing post-wait kernel extension (AT&T Unix, AIX), when semaphores are not used by Oracle at all.

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