今天碰到一个tc 类型的enqueue锁。以前没见过，后来上metalink一查发现是tablespace checkpoint的意思。

顺便看到以下新增加的enqueue类型，收藏一下。

AF :

"This enqueue is used to serialize access to an advisor task"

AS :

"Synchronizes new service activation"

CT :
"A general class of locks used by change tracking for
various purposes"

DP :

"Synchronizes access to LDAP parameters"

FU :

"This enqueue is used to serialize the capture of the DB Feature Usage and High Water Mark Statistics"

IT :

"This enqueue is used for making temp table meta-data pinning, recreation code for slave on other instance atomic so that deadlock won't happen."

JS :

"Synchronizes accesses to the job cache"

MW :

"This enqueue is used to serialize the calibration of the
manageability schedules with the Maintenance Window "

RO :

"Coordinates flushing of multiple objects"

RS :

"Lock held by a space reclaimable operation to allow other operations to wait for it"

TB :

"Synchronizes writes to the SQL Tuning Base Existence Cache"

TL :

"Serializes threshold log table read and update"

TQ :

"Synchronizes access to queue table"

WF :

"This enqueue is used to serialize the flushing of snapshots"

WP :

"This enqueue handles concurrency between purging and baselines"

TC :

"Lock held to guarantee uniqueness of a tablespace checkpoint"