OCI Function Server Round-Trips

C OCI Function Server Round-Trips

This appendix provides information about server round-trips incurred during various OCI calls.

This information can help programmers to determine the most efficient way to accomplish a particular task in an application. A server round-trip is defined as the trip from the client to the server and back to the client.

When using client-side SQL, OCI provides:

Enhanced array data manipulation language (DML) capability for arrays
Ability to associate a commit request with a run to reduce round-trips
Optimization for queries using transparent prefetch buffers to reduce round-trips

As is often the case, there are tradeoffs. For example, for queries the trade off is often arraysize and prefetch size versus the number of underlying fetches.

Relational Function Round-Trips

Describes for each OCI relational function the number of server round-trips.

Table C-1 lists the number of server round-trips required by each OCI relational function.

Table C-1 Server Round-Trips for Relational Operations

Function	Number of Server Round-Trips
`OCIBreak()`	1
`OCIDBShutdown()`	1
`OCIDBStartup()`	1
`OCIEnvCreate()`	0
`OCIEnvInit()`	0
`OCIErrorGet()`	0
`OCIInitialize()`	0
`OCILdaToSvcCtx()`	0
`OCILogoff()`	1
`OCILogon()`	1
`OCILogon2()`	Connection pool or session pool: same as OCISessionGet() Normal: 2 (depends on authentication and TAF situation)
`OCIPasswordChange()`	1
`OCIPing()`	1
`OCIReset()`	0
`OCIServerAttach()`	1
`OCIServerDetach()`	1
`OCIServerVersion()`	1
`OCISessionBegin()`	1
`OCISessionEnd()`	1
`OCISessionGet()`	Session pool: 0 - increment of logins. Connection pool: 1 to (1+ (increment * logins)). Depends on cache hit: one for the user session, optional increment for primary sessions. Normal: 1 login
`OCISessionPoolCreate()`	sessMin * logins
`OCISessionPoolDestroy()`	Sessions in cache * logoffs
`OCISessionRelease()`	Session pooling: 0, except when explicit session destroys flag set Normal: 1 login
`OCIStmtExecute()`	1
`OCIStmtFetch()`	0 or 1
`OCIStmtFetch2()`	0 in prefetch, otherwise 1
`OCIStmtGetPieceInfo()`	1
`OCIStmtPrepare()`	0
`OCIStmtPrepare2()`	0
`OCIStmtSetPieceInfo()`	0
`OCISvcCtxToLda()`	0
`OCITerminate()`	1
`OCITransCommit()`	1
`OCITransDetach()`	1
`OCITransForget()`	1
`OCITransPrepare()`	1
`OCItransRollback()`	1
`OCITransStart()`	1
`OCIUserCallbackGet()`	0
`OCIUserCallbackRegister()`	0

LOB Function Round-Trips

Describes for each OCI LOB function the number of server round-trips.

Table C-2 lists the server round-trips incurred by the OCILob calls.

Note:

To minimize the number of round-trips, you can use the data interface for LOBs. You can bind or define character data for a CLOB column or RAW data for a BLOB column.

For calls whose number of round-trips is "0 or 1," if LOB buffering is on, and the request can be satisfied in the client, no round-trips are incurred.

Table C-2 Server Round-Trips for OCILob Calls

Function	Number of Server Round-Trips
`OCILobAppend()`	1
`OCILobArrayRead()`	1
`OCILobArraywrite()`	1
`OCILobAssign()`	0
`OCILobCharSetForm()`	0
`OCILobCharSetId()`	0
`OCILobClose()`	1
`OCILobCopy()`	1
`OCILobCopy2()`	1
`OCILobCreateTemporary()`	1
`OCILobDisableBuffering()`	0
`OCILobEnableBuffering()`	0
`OCILobErase()`	1
`OCILobErase2()`	1
`OCILobFileClose()`	1
`OCILobFileCloseAll()`	1
`OCILobFileExists()`	1
`OCILobFileGetName()`	0
`OCILobFileIsOpen()`	1
`OCILobFileOpen()`	1
`OCILobFileSetName()`	0
`OCILobFlushBuffer()`	1 for each modified page in the buffer for this LOB
`OCILobFreeTemporary()`	1
`OCILobGetChunkSize()`	1
`OCILobGetLength()`	1
`OCILobGetLength2()`	1
`OCILobGetStorageLimit()`	1
`OCILobIsEqual()`	0
`OCILobIsOpen()`	1
`OCILobIsTemporary()`	0
`OCILobLoadFromFile()`	1
`OCILobLoadFromFile2()`	1
`OCILobLocatorAssign()`	1 round-trip if either the source or the destination locator refers to a temporary LOB
`OCILobLocatorIsInit()`	0
`OCILobOpen()`	1
`OCILobRead()`	0 or 1
`OCILobRead2()`	0 or 1
`OCILobTrim()`	1
`OCILobTrim2()`	1
`OCILobWrite()`	0 or 1
`OCILobWrite2()`	0 or 1
`OCILobWriteAppend()`	0 or 1
`OCILobWriteAppend2()`	0 or 1

Object and Cache Function Round-Trips

Describes for each OCI object and cache function the number of server round-trips.

Table C-3 lists the number of server round-trips required for the object and cache functions. These values assume the cache is in a warm state, meaning that the type descriptor objects required by the application have been loaded.

Table C-3 Server Round-Trips for Object and Cache Functions

Function	Number of Server Round-Trips
`OCICacheFlush()`	1
`OCICacheFree()`	0
`OCICacheRefresh()`	1
`OCICacheUnmark()`	0
`OCICacheUnpin()`	0
`OCIObjectArrayPin()`	1
`OCIObjectCopy()`	0
`OCIObjectExists()`	0
`OCIObjectFlush()`	1
`OCIObjectFree()`	0
`OCIObjectGetInd()`	0
`OCIObjectGetObjectRef()`	0
`OCIObjectGetTypeRef()`	0
`OCIObjectIsDirty()`	0
`OCIObjectIsLocked()`	0
`OCIObjectLock()`	1
`OCIObjectMarkDelete()`	0
`OCIObjectMarkDeleteByRef()`	0
`OCIObjectMarkUpdate()`	0
`OCIObjectNew()`	0
`OCIObjectPin()`	1; 0 if the desired object is already in cache
`OCIObjectPinCountReset()`	0
`OCIObjectPinTable()`	1
`OCIObjectRefresh()`	1
`OCIObjectUnmark()`	0
`OCIObjectUnmarkByRef()`	0
`OCIObjectUnpin()`	0

Describe Operation Round-Trips

Describes for each OCI operation function the number of server round-trips.

Table C-4 lists the number of server round-trips required by OCIDescribeAny(), OCIAttrGet(), and OCIParamGet().

Table C-4 Server Round-Trips for Describe Operations

Function Number of Server Round-Trips

Function	Number of Server Round-Trips
`OCIAttrGet()`	2 round-trips to describe a type if the type objects are not in the object cache 1 round-trip for each collection element, or each type attribute, method, or method argument descriptor. 1 more round-trip if using `OCI_ATTR_TYPE_NAME`, or `OCI_ATTR_SCHEMA_NAME` on the collection element, type attribute, or method argument. 0 if all the type objects to be described are already in the object cache following the first `OCIAttrGet()` call.
`OCIDescribeAny()`	1 round-trip to get the `REF` of the type descriptor object
`OCIParamGet()`	0

OCIAttrGet()

2 round-trips to describe a type if the type objects are not in the object cache

1 round-trip for each collection element, or each type attribute, method, or method argument descriptor. 1 more round-trip if using OCI_ATTR_TYPE_NAME, or OCI_ATTR_SCHEMA_NAME on the collection element, type attribute, or method argument.

0 if all the type objects to be described are already in the object cache following the first OCIAttrGet() call.

OCIDescribeAny()

1 round-trip to get the REF of the type descriptor object

OCIParamGet()

Data Type Mapping and Manipulation Function Round-Trips

Describes for each OCI data type mapping and manipulation function the number of server round-trips.

Table C-5 lists the number of round-trips for the data type mapping and manipulation functions. The asterisks in the table indicate that all functions with a particular prefix incur the same number of server round-trips. For example, OCINumberAdd(), OCINumberPower(), and OCINumberFromText() all incur zero server round-trips.

Table C-5 Server Round-Trips for Data Type Manipulation Functions

Function	Number of Server Round-Trips
`OCIColl*()`	0; 1 if the collection is not loaded in the cache
`OCIDate*()`	0
`OCIIter*()`	0; 1 if the collection is not loaded in the cache
`OCINumber*()`	0
`OCIRaw*()`	0
`OCIRef*()`	0
`OCIString*()`	0
`OCITable*()`	0; 1 if the nested table is not loaded in the cache

Any Type and Data Function Round-Trips

Describes for each OCI Any Type and Data function the number of server round-trips.

Table C-6 lists the number of server round-trips required by Any Type and Data functions. The functions not listed do not generate any round-trips.

Table C-6 Server Round-Trips for Any Type and Data Functions

Function	Number of Server Round-Trips
`OCIAnyDataAttrGet()`	0; 1 if the type information is not loaded in the cache
`OCIAnyDataAttrSet()`	0; 1 if the type information is not loaded in the cache
`OCIAnyDataCollGetElem()`	0; 1 if the type information is not loaded in the cache

Other Local Functions

Describes for each OCI other local function the number of server round-trips.

Table C-7 lists the functions that are local and do not require a server round-trip.

Table C-7 Locally Processed Functions

Local Function Name	Notes
`OCIAttrGet()`	When describing an object type, this call makes one round-trip to fetch the type descriptor object.
`OCIAttrSet()`
`OCIBindArrayOfStruct()`
`OCIDefineArrayOfStruct()`
`OCIBindByName()`
`OCIBindByPos()`
`OCIBindDynamic()`
`OCIBindObject()`
`OCIDefineByPos()`
`OCIDefineDynamic()`
`OCIDefineObject()`
`OCIDescriptorAlloc()`
`OCIDescriptorFree()`
`OCIEnvCreate()`
`OCIEnvInit()`
`OCIErrorGet()`
`OCIHandleAlloc()`
`OCIHandleFree()`
`OCILdaToSvcCtx()`
`OCIStmtGetBindInfo()`
`OCIStmtPrepare()`
`OCIStmtRelease()`
`OCIStmtPrepare2()`
`OCISvcCtxToLda()`