Why 'gz.org_opengrok' file is created after indexing?

[js3416]

Hi team,

I found 'gz.org_opengrok' files are created after index on my project.
-rwxrwxrwx 1 xxxx users 92 Jun 21 21:58 Makefile
-rw-rw-rw- 1 xxxx users 374 Jun 27 15:18 Makefile.gz.org_opengrok
-rw-rw-rw- 1 xxxx users 20 Jun 27 15:18 Makefile.gz.org_opengrok.gz.org_opengrok

Why these files are existed?

I made symbolic link xref file as below. It could be a cuase?

/local2/mnt/opengrok/data$ ls -l
lrwxrwxrwx 1 xxxx users 26 Jun 15 18:42 xref -> /local2/mnt/opengrok/src/

Thanks.

[vladak]

what OpenGrok version is this ?

[js3416]

The version is 1.5.11.