Save-while-active object locking rules

The object locking rules that the system uses for save-while-active requests are less restrictive than the rules it uses for other save operations.

These object locking rules allow users to perform update operations and use most object-level commands after the system performs checkpoint processing. Generally, the system keeps a shared, no update (*SHRNUP) lock on the objects through the checkpoint processing. After the checkpoint completes, the system unlocks most of the objects. Other objects remain allocated with a shared for read (*SHRRD) lock.

The following table shows the locks a normal save operation holds, by a save-while-active operation during checkpoint processing, and by a save-while-active operation after checkpoint processing is complete.

Table 1. Lock type needed for save operation
		Save-While-Active
Object Type	SAVACT(*NO)	Establish Checkpoint	After Checkpoint
Most object types	*SHRNUP	*SHRNUP	None
Configuration object	None	¹	¹
Data area	*SHRNUP	*SHRRD⁶	None
Database members	*SHRNUP	*SHRRD	None
Document	*SHRNUP	*SHRRD	None
Folder	*SHRRD	*SHRRD	None
Job queue	*SHRRD	*SHRRD	None
Journal	*SHRRD	*SHRRD	None
Journal receiver	*SHRRD	*SHRRD	*SHRRD
Library, when the library or an object in it is being saved	*SHRUPD	*SHRUPD	*SHRRD
Output queue	*SHRRD	*SHRRD	None
Product load	*SHRNUP	*SHRNUP	*SHRRD
Spooled file	*EXCL	*EXCL	⁵
System resource management object	*SHRNUP	¹	¹
User profiles, authorization lists, and authority holders	*SHRRD	¹	¹
Object, if STG(*FREE) is specified	*EXCL²	¹	¹
Objects in directories	Share with readers	Share with readers^{3, 4}	Share with readers and writers³
¹ The save-while-active function is not available when saving these objects. ² Applies to document, file, journal receiver, module, program, SQL package, and service program. Other types remain as listed previously. ³ Objects in QNTC are not synchronized with SAVACT(SYNC). Furthermore, all locks for these file systems will be released before the checkpoint message is sent. ⁴ Objects that are saved with SAVACTOPT(ALWCKPWRT) and have the QP0L_ATTR_ALWCKPWRT system attribute set, have an implied share with readers and writers lock. ⁵ A lock is held that prevents another save action against the spooled file. All other spooled file actions, such as displaying, copying, deleting, and printing, are allowed. ⁶ An internal lock is also held that prevents changes to the object during save-while-active checkpoint processing.

These locking rules pertain to object-level locks and not database record-level locks. The locking rules allow the opening and closing of database file members and any record-level I/O operations to database file members during any phase of the save-while-active operation.