{ "date": "2017-06-15T15:15:16", "slug": "12c-nssn-process-for-data-guard-sync-transport", "link": "https://www.dbi-services.com/blog/12c-nssn-process-for-data-guard-sync-transport/", "title": { "rendered": "12c NSSn process for Data Guard SYNC transport" }, "content": { "rendered": "

By Franck Pachot

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\nIn a previous post https://www.dbi-services.com/blog/dataguard-wait-events-have-changed-in-12c/ I mentioned the new processes NSA for ASYNC transport and NSS for SYNC transport. I’m answering a bit late to a comment about the number of processes: yes there is one NSSn process per LOG_ARCHIVE_DEST_n destination in SYNC and the numbers match.
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Here is my configuration with two physical standby:

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DGMGRL> show configuration\n \nConfiguration - orcl\n \n  Protection Mode: MaxPerformance\n  Members:\n  orcla - Primary database\n    orclb - Physical standby database\n    orclc - Physical standby database\n \nFast-Start Failover: DISABLED\n \nConfiguration Status:\nSUCCESS   (status updated 56 seconds ago)
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Both are in SYNC:

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DGMGRL> show database orclb logxptmode;\n  LogXptMode = 'sync'\nDGMGRL> show database orclc logxptmode;\n  LogXptMode = 'sync'
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I can see two NSS processes:

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DGMGRL> host ps -edf | grep --color=auto ora_nss[0-9]\nExecuting operating system command(s):\" ps -edf | grep --color=auto ora_nss[0-9]\"\noracle    4952     1  0 16:05 ?        00:00:00 ora_nss3_ORCLA\noracle    5322     1  0 16:17 ?        00:00:00 ora_nss2_ORCLA
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Here are the two log archive dest:

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SQL> select name,value from v$parameter where regexp_like(name,'^log_archive_dest_[23]$');\nNAME                VALUE                                                                                                                                                                     \n----                -----\nlog_archive_dest_2  service=\"ORCLB\", SYNC AFFIRM delay=0 optional compression=disable max_failure=0 max_connections=1 reopen=300 db_unique_name=\"orclb\" net_timeout=30, valid_for=(online_logfile,all_roles)\nlog_archive_dest_3  service=\"ORCLC\", SYNC AFFIRM delay=0 optional compression=disable max_failure=0 max_connections=1 reopen=300 db_unique_name=\"orclc\" net_timeout=30, valid_for=(online_logfile,all_roles)
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I set the 3rd one in ASYNC:

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DGMGRL> edit database orclc set property logxptmode=ASYNC;\nProperty \"logxptmode\" updated
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The NSS3 has stopped:

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DGMGRL> host ps -edf | grep --color=auto ora_nss[0-9]\nExecuting operating system command(s):\" ps -edf | grep --color=auto ora_nss[0-9]\"\noracle    5322     1  0 16:17 ?        00:00:00 ora_nss2_ORCLA
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I set the 2nd destination to ASYNC:

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DGMGRL> edit database orclb set property logxptmode=ASYNC;\nProperty \"logxptmode\" updated
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The NSS2 has stopped:

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DGMGRL> host ps -edf | grep --color=auto ora_nss[0-9]\nExecuting operating system command(s):\" ps -edf | grep --color=auto ora_nss[0-9]\"
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Now starting the 3rd destination first:

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DGMGRL> edit database orclc set property logxptmode=SYNC;\nProperty \"logxptmode\" updated
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I can see that nss3 has started as it is the log_archive_dest_3 which is in SYNC now:

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DGMGRL> host ps -edf | grep --color=auto ora_nss[0-9]\nExecuting operating system command(s):\" ps -edf | grep --color=auto ora_nss[0-9]\"\noracle    5368     1  0 16:20 ?        00:00:00 ora_nss3_ORCLA
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Then starting the second one:

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DGMGRL> edit database orclb set property logxptmode=SYNC;\nProperty \"logxptmode\" updated
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Here are the two processes:

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\nDGMGRL> host ps -edf | grep --color=auto ora_nss[0-9]\nExecuting operating system command(s):\" ps -edf | grep --color=auto ora_nss[0-9]\"\noracle    5368     1  0 16:20 ?        00:00:00 ora_nss3_ORCLA\noracle    5393     1  0 16:20 ?        00:00:00 ora_nss2_ORCLA
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So if you see some SYNC Remote Write events in ASH, look at the program name to know which destination it is.

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