{"id":1611,"date":"2015-10-05T15:53:13","date_gmt":"2015-10-05T20:53:13","guid":{"rendered":"https:\/\/bijoos.com\/oraclenotes\/?p=1611"},"modified":"2026-02-07T15:34:43","modified_gmt":"2026-02-07T21:34:43","slug":"critical-background-processes-in-oracle-database-12c","status":"publish","type":"post","link":"https:\/\/bijoos.com\/oraclenotes\/2015\/1611\/","title":{"rendered":"Critical Background Processes in Oracle Database 12c"},"content":{"rendered":"

There are several background processes running when you start Oracle Database 12c instance. Here is an example from one of the 12.1.0.2 instances.<\/p>\n

 <\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
\n

\u00a0ora_acms_bt9prod1<\/p>\n<\/td>\n

\u00a0ora_lreg_bt9prod1<\/td>\nora_p00w_bt9prod1<\/td>\n<\/tr>\n
\u00a0ora_aqpc_bt9prod1<\/td>\n\u00a0ora_m000_bt9prod1<\/td>\n\u00a0ora_p00x_bt9prod1<\/td>\n<\/tr>\n
\u00a0ora_asmb_bt9prod1<\/td>\n\u00a0ora_mark_bt9prod1<\/td>\n\u00a0ora_p00y_bt9prod1<\/td>\n<\/tr>\n
\u00a0ora_cjq0_bt9prod1<\/td>\n\u00a0ora_mman_bt9prod1<\/td>\n\u00a0ora_p00z_bt9prod1<\/td>\n<\/tr>\n
\u00a0ora_ckpt_bt9prod1<\/td>\n\u00a0ora_mmnl_bt9prod1<\/td>\n\u00a0ora_ping_bt9prod1<\/td>\n<\/tr>\n
\u00a0ora_dbrm_bt9prod1<\/td>\n\u00a0ora_mmon_bt9prod1<\/td>\n\u00a0ora_pmon_bt9prod1<\/td>\n<\/tr>\n
\u00a0ora_dbw0_bt9prod1<\/td>\n\u00a0ora_o000_bt9prod1<\/td>\n\u00a0ora_ppa6_bt9prod1<\/td>\n<\/tr>\n
\u00a0ora_dbw1_bt9prod1<\/td>\n\u00a0ora_p000_bt9prod1<\/td>\n\u00a0ora_ppa7_bt9prod1<\/td>\n<\/tr>\n
\u00a0ora_dbw2_bt9prod1<\/td>\n\u00a0ora_p001_bt9prod1<\/td>\n\u00a0ora_psp0_bt9prod1<\/td>\n<\/tr>\n
\u00a0ora_dbw3_bt9prod1<\/td>\n\u00a0ora_p002_bt9prod1<\/td>\n\u00a0ora_pxmn_bt9prod1<\/td>\n<\/tr>\n
\u00a0ora_dbw4_bt9prod1<\/td>\n\u00a0ora_p003_bt9prod1<\/td>\n\u00a0ora_q001_bt9prod1<\/td>\n<\/tr>\n
\u00a0ora_dbw5_bt9prod1<\/td>\n\u00a0ora_p004_bt9prod1<\/td>\n\u00a0ora_q003_bt9prod1<\/td>\n<\/tr>\n
\u00a0ora_dbw6_bt9prod1<\/td>\n\u00a0ora_p005_bt9prod1<\/td>\n\u00a0ora_q006_bt9prod1<\/td>\n<\/tr>\n
\u00a0ora_dbw7_bt9prod1<\/td>\n\u00a0ora_p006_bt9prod1<\/td>\n\u00a0ora_q008_bt9prod1<\/td>\n<\/tr>\n
\u00a0ora_dbw8_bt9prod1<\/td>\n\u00a0ora_p007_bt9prod1<\/td>\n\u00a0ora_q009_bt9prod1<\/td>\n<\/tr>\n
\u00a0ora_dbw9_bt9prod1<\/td>\n\u00a0ora_p008_bt9prod1<\/td>\n\u00a0ora_q00a_bt9prod1<\/td>\n<\/tr>\n
\u00a0ora_dbwa_bt9prod1<\/td>\n\u00a0ora_p009_bt9prod1<\/td>\n\u00a0ora_q00b_bt9prod1<\/td>\n<\/tr>\n
\u00a0ora_dbwb_bt9prod1<\/td>\n\u00a0ora_p00a_bt9prod1<\/td>\n\u00a0ora_qm00_bt9prod1<\/td>\n<\/tr>\n
\u00a0ora_dbwc_bt9prod1<\/td>\n\u00a0ora_p00b_bt9prod1<\/td>\n\u00a0ora_qm02_bt9prod1<\/td>\n<\/tr>\n
\u00a0ora_dbwd_bt9prod1<\/td>\n\u00a0ora_p00c_bt9prod1<\/td>\n\u00a0ora_qm03_bt9prod1<\/td>\n<\/tr>\n
\u00a0ora_dbwe_bt9prod1<\/td>\n\u00a0ora_p00d_bt9prod1<\/td>\n\u00a0ora_qm05_bt9prod1<\/td>\n<\/tr>\n
\u00a0ora_dbwf_bt9prod1<\/td>\n\u00a0ora_p00e_bt9prod1<\/td>\n\u00a0ora_rbal_bt9prod1<\/td>\n<\/tr>\n
\u00a0ora_dia0_bt9prod1<\/td>\n\u00a0ora_p00f_bt9prod1<\/td>\n\u00a0ora_rcbg_bt9prod1<\/td>\n<\/tr>\n
\u00a0ora_diag_bt9prod1<\/td>\n\u00a0ora_p00g_bt9prod1<\/td>\n\u00a0ora_reco_bt9prod1<\/td>\n<\/tr>\n
\u00a0ora_gcr0_bt9prod1<\/td>\n\u00a0ora_p00h_bt9prod1<\/td>\n\u00a0ora_rms0_bt9prod1<\/td>\n<\/tr>\n
\u00a0ora_gen0_bt9prod1<\/td>\n\u00a0ora_p00i_bt9prod1<\/td>\n\u00a0ora_rmv0_bt9prod1<\/td>\n<\/tr>\n
\u00a0ora_gtx0_bt9prod1<\/td>\n\u00a0ora_p00j_bt9prod1<\/td>\n\u00a0ora_rmv1_bt9prod1<\/td>\n<\/tr>\n
\u00a0ora_lck0_bt9prod1<\/td>\n\u00a0ora_p00k_bt9prod1<\/td>\n\u00a0ora_rmv2_bt9prod1<\/td>\n<\/tr>\n
\u00a0ora_lck1_bt9prod1<\/td>\n\u00a0ora_p00l_bt9prod1<\/td>\n\u00a0ora_rsmn_bt9prod1<\/td>\n<\/tr>\n
\u00a0ora_lg00_bt9prod1<\/td>\n\u00a0ora_p00m_bt9prod1<\/td>\n\u00a0ora_smco_bt9prod1<\/td>\n<\/tr>\n
\u00a0ora_lg01_bt9prod1<\/td>\n\u00a0ora_p00n_bt9prod1<\/td>\n\u00a0ora_smon_bt9prod1<\/td>\n<\/tr>\n
\u00a0ora_lgwr_bt9prod1<\/td>\n\u00a0ora_p00o_bt9prod1<\/td>\n\u00a0ora_tmon_bt9prod1<\/td>\n<\/tr>\n
\u00a0ora_lmd0_bt9prod1<\/td>\n\u00a0ora_p00p_bt9prod1<\/td>\n\u00a0ora_tt00_bt9prod1<\/td>\n<\/tr>\n
\u00a0ora_lmd1_bt9prod1<\/td>\n\u00a0ora_p00q_bt9prod1<\/td>\n\u00a0ora_vkrm_bt9prod1<\/td>\n<\/tr>\n
\u00a0ora_lmhb_bt9prod1<\/td>\n\u00a0ora_p00r_bt9prod1<\/td>\n\u00a0ora_vktm_bt9prod1<\/td>\n<\/tr>\n
\u00a0ora_lmon_bt9prod1<\/td>\n\u00a0ora_p00s_bt9prod1<\/td>\n\u00a0ora_w008_bt9prod1<\/td>\n<\/tr>\n
\u00a0ora_lms0_bt9prod1<\/td>\n\u00a0ora_p00t_bt9prod1<\/td>\n\u00a0ora_w009_bt9prod1<\/td>\n<\/tr>\n
\u00a0ora_lms1_bt9prod1<\/td>\n\u00a0ora_p00u_bt9prod1<\/td>\n <\/td>\n<\/tr>\n
\u00a0ora_lms2_bt9prod1<\/td>\n\u00a0ora_p00v_bt9prod1<\/td>\n <\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Which processes are critical for database operation? In other words, if you terminate one of these processes knowingly or unknowingly, will the instance terminate?<\/p>\n

The critical processes required for basic database operation are:<\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
Acronym<\/strong><\/td>\nProcess Name<\/strong><\/td>\nDescription<\/strong><\/td>\n<\/tr>\n
CKPT<\/td>\nCheckpoint Process<\/td>\nSignals DBWn at checkpoints and updates all the data files and control files of the database to indicate the most recent checkpoint<\/td>\n<\/tr>\n
DBWn<\/td>\nDatabase Writer Process<\/td>\nWrites modified blocks from the database buffer cache to the data files. There can be 1 to 100 Database Writer Processes. The names of the first 36 Database Writer Processes are DBW0-DBW9 and DBWa-DBWz. The names of the 37th through 100th Database Writer Processes are BW36-BW99.<\/td>\n<\/tr>\n
BWnn<\/td>\nDatabase Writer Process<\/td>\nThe names of the 37th through 100th Database Writer Processes are BW36-BW99.<\/td>\n<\/tr>\n
DIAG<\/td>\nDiagnostic Capture Process<\/td>\nPerforms diagnostic dumps and executes global oradebug commands.<\/td>\n<\/tr>\n
DIA0<\/td>\nDiagnostic Process 0 (although 10 possible, only 0 is currently used)<\/td>\nResponsible for hang detection and deadlock resolution. Triggers DIAG to perform diagnostic tasks.<\/td>\n<\/tr>\n
GEN0<\/td>\nGeneral Task Execution Process<\/td>\nPerforms required tasks including SQL and DML.<\/td>\n<\/tr>\n
CSnn<\/td>\nI\/O Calibration Process<\/td>\nIssues I\/Os to storage as part of storage calibration. There is one slave process per CPU on each node of the database.<\/td>\n<\/tr>\n
LREG<\/td>\nListener Registration Process<\/td>\nLREG notifies the listeners about instances, services, handlers, and endpoint.<\/td>\n<\/tr>\n
LGWR<\/td>\nLog Writer Process<\/td>\nWrites the log buffer out to the redo logs.<\/td>\n<\/tr>\n
OFSD<\/td>\nOracle File Server Background Process<\/td>\nThis background process listens for new file system requests, both management (like mount, unmount, and export) and I\/O requests, and executes them using Oracle threads.<\/td>\n<\/tr>\n
PMON<\/td>\nProcess Monitor<\/td>\nRecovers failed process resources. If Shared Server architecture is used, PMON monitors and restarts any failed dispatcher or server processes.<\/td>\n<\/tr>\n
SMON<\/td>\nSystem Monitor Process<\/td>\nPerforms critical tasks such as instance recovery and dead transaction recovery, and maintenance tasks such as temporary space reclamation, data dictionary cleanup, and undo tablespace management<\/td>\n<\/tr>\n
VKTM<\/td>\nVirtual Keeper of Time Process<\/td>\nResponsible for providing a wall-clock time (updated every second) and reference-time counter (updated every 20ms and available only when running at elevated priority).<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

 <\/p>\n","protected":false},"excerpt":{"rendered":"

There are several background processes running when you start Oracle Database 12c instance. Here is an example from one of the 12.1.0.2 instances.   \u00a0ora_acms_bt9prod1 \u00a0ora_lreg_bt9prod1 ora_p00w_bt9prod1 \u00a0ora_aqpc_bt9prod1 \u00a0ora_m000_bt9prod1 \u00a0ora_p00x_bt9prod1 \u00a0ora_asmb_bt9prod1 \u00a0ora_mark_bt9prod1 \u00a0ora_p00y_bt9prod1 \u00a0ora_cjq0_bt9prod1 \u00a0ora_mman_bt9prod1 \u00a0ora_p00z_bt9prod1 \u00a0ora_ckpt_bt9prod1 \u00a0ora_mmnl_bt9prod1 \u00a0ora_ping_bt9prod1 \u00a0ora_dbrm_bt9prod1 \u00a0ora_mmon_bt9prod1 \u00a0ora_pmon_bt9prod1 \u00a0ora_dbw0_bt9prod1 \u00a0ora_o000_bt9prod1 \u00a0ora_ppa6_bt9prod1 \u00a0ora_dbw1_bt9prod1 \u00a0ora_p000_bt9prod1 \u00a0ora_ppa7_bt9prod1 \u00a0ora_dbw2_bt9prod1 \u00a0ora_p001_bt9prod1 \u00a0ora_psp0_bt9prod1 \u00a0ora_dbw3_bt9prod1 \u00a0ora_p002_bt9prod1 \u00a0ora_pxmn_bt9prod1 \u00a0ora_dbw4_bt9prod1 … Read more<\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[133],"tags":[],"class_list":["post-1611","post","type-post","status-publish","format-standard","hentry","category-oracledb"],"acf":[],"jetpack_featured_media_url":"","jetpack-related-posts":[],"jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/bijoos.com\/oraclenotes\/wp-json\/wp\/v2\/posts\/1611","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/bijoos.com\/oraclenotes\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/bijoos.com\/oraclenotes\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/bijoos.com\/oraclenotes\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/bijoos.com\/oraclenotes\/wp-json\/wp\/v2\/comments?post=1611"}],"version-history":[{"count":1,"href":"https:\/\/bijoos.com\/oraclenotes\/wp-json\/wp\/v2\/posts\/1611\/revisions"}],"predecessor-version":[{"id":3016,"href":"https:\/\/bijoos.com\/oraclenotes\/wp-json\/wp\/v2\/posts\/1611\/revisions\/3016"}],"wp:attachment":[{"href":"https:\/\/bijoos.com\/oraclenotes\/wp-json\/wp\/v2\/media?parent=1611"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/bijoos.com\/oraclenotes\/wp-json\/wp\/v2\/categories?post=1611"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/bijoos.com\/oraclenotes\/wp-json\/wp\/v2\/tags?post=1611"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}