$ java -Xlog:cds -version | grep Opened.archive
[0.006s][info][cds] Opened archive /work/images/jdk/lib/server/classes.jsa.
java version "18-internal" 2022-03-15
Java(TM) SE Runtime Environment (build 18-internal+0-adhoc.iklam.open)
Java HotSpot(TM) 64-Bit Server VM (build 18-internal+0-adhoc.iklam.open, mixed mode, sharing)

$ ls -l /work/images/jdk/lib/server/classes.jsa
-r--r--r-- 1 iklam dba 13410304 Nov 9 20:25 /work/images/jdk/lib/server/classes.jsa
$ java -XX:ArchiveClassesAtExit=/work/images/jdk/lib/server/classes.jsa -Xlog:cds -version
[.......]
[0.172s][info][cds] Dumping shared data to file:
[0.172s][info][cds] /work/images/jdk/lib/server/classes.jsa
[0.172s][info][cds] Shared file region (rw ) 0: 45352 bytes, addr 0x0000000800ba9000 file offset 0x00001000 crc 0x165e738d
[0.173s][info][cds] Shared file region (ro ) 1: 53944 bytes, addr 0x0000000800bb5000 file offset 0x0000d000 crc 0x728b4f18
[0.173s][info][cds] Shared file region (bm ) 2: 1616 bytes, addr 0x0000000000000000 file offset 0x0001b000 crc 0xf9e817cf

$ ls -l /work/images/jdk/lib/server/classes.jsa
-r--r--r-- 1 iklam dba 114688 Nov 14 23:52 /work/images/jdk/lib/server/classes.jsa

$ java -Xlog:cds -version
[0.005s][info][cds] trying to map /work/images/jdk/lib/server/classes.jsa
[0.005s][info][cds] Opened archive /work/images/jdk/lib/server/classes.jsa.
[0.005s][info][cds] _magic expected: 0xf00baba2
[0.005s][info][cds] actual: 0xf00baba8
[0.005s][info][cds] UseSharedSpaces: The shared archive file has a bad magic number.
[0.005s][info][cds] UseSharedSpaces: Unable to map shared spaces
java version "18-internal" 2022-03-15
Java(TM) SE Runtime Environment (build 18-internal+0-adhoc.iklam.open)
Java HotSpot(TM) 64-Bit Server VM (build 18-internal+0-adhoc.iklam.open, mixed mode)